Peptide purification method using sulfonate compound

ABSTRACT

A method for purifying a target peptide may include mixing a peptide product obtained through a peptide synthesis with a solvent in the presence of a sulfonic acid compound to obtain a solid; and performing a solid-liquid separation to collect the solid.

TECHNICAL FIELD

The present application relates to a method for purifying a target peptide from peptide product obtained by peptide synthesis, and a medicament comprising the target peptide obtained by the purification method.

BACKGROUND ART

Peptides with relatively few amino acid residues (usually less than or equal to 30 residues) are commonly produced by organic chemical synthesis (for example, Patent Document 1). Examples of the organic chemical synthesis method include solid-phase and liquid-phase methods, in which peptide elongation reactions consisting of coupling reaction of N-protected amino acid with C-protected peptide (C-protected amino acid in a case of dipeptide formation) followed by N-terminal deprotection reaction are repeated. In the organic chemical synthesis methods, since various analogue peptides are also synthesized due to partial duplication, partial omission, etc. of the peptide elongation reaction, it is required to separate the generated target peptide from these analogue peptides. However, the physicochemical properties of analogue peptides are often very similar to those of the target peptide, making their separation very difficult. It is desired to provide a method for effectively separating a target peptide and analogue peptides in order to obtain a purified target peptide.

Peptides comprising more amino acid residues (usually over 30 residues) are commonly produced by fermentation (for example, Patent Document 2). In this case, analogue peptides, for example, having amino acid replacement(s) may contaminate the target one, and the separation of these peptides having very similar properties is a serious problem.

At present, even in the case where the scale is increased, the purification of peptide is generally performed by a preparative high performance liquid chromatography method, which requires a large cost. It is desired to provide a method for effectively separating/removing analogue peptide(s) from a mixture of a target peptide and analogue peptide(s) thereof, for replacing or supplementing the preparative high performance liquid chromatography.

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: JP 2018-52933 A -   Patent Document 2: JP 2016-190851 A

The disclosures of the prior art documents cited herein are incorporated herein by reference in their entirety.

SUMMARY Technical Problem

An objective of the present application is to provide a method for purifying a target peptide comprising removing analogue peptide(s) from a mixture comprising the target peptide and the analogue peptide(s), obtained through peptide synthesis. Another objective of the present application is to provide a peptide purification method for replacing or supplementing conventional peptide purification method(s).

Solution to Problem

As a result of studies to solve the above problems, the present inventors have found that when a synthetic peptide product of a target peptide comprising an analogue peptide is mixed with a sulfonic acid compound having a certain structure in the presence of a solvent followed by a solid-liquid separation, the purity (absolute purity, except the sulfonic acid compounds) of the target peptide is improved and a solid product comprising the sulfonate salt of the target peptide having a reduced ratio of the analogue peptide is provided, thereby reaching the present invention.

The invention of the present application is explained in detail below.

[Aspect 1] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 1-1] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation one minute or more after the mixing to collect the solid.

[Aspect 1-2] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid, wherein the solvent comprises water; an alcohol compound; acetonitrile; an ether compound; a ketone compound; an ester compound; a hydrocarbon compound; DMSO; an amide compound; a halogenated hydrocarbon; or a mixture thereof;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 1-3] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation to collect the solid;

(3) washing the solid.

[Aspect 1-4] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound at 0 to 50° C. to provide a solid;

(2) performing a solid-liquid separation at 0 to 50° C. to collect the solid.

[Aspect 1-5] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid, wherein the weight ratio of the solvent to the target peptide (the weight of solvent/the weight of target peptide) is 1 to 100000;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 1-6] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid, wherein the molar ratio of the sulfonic acid compound to the target peptide is 0.1 to 50;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 1-7] A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a sulfonic acid compound in the presence of a solvent;

(2) separating the resulting solid from the liquid phase to collect the resulting solid.

[Aspect 2] The method according to any one of Aspects 1, and 1-1 to 1-7, wherein the sulfonic acid compound is represented by formula (I):

wherein:

A is C₆₋₁₄aryl (for example, C₆₋₁₃aryl, C₆₋₁₀aryl) which may be substituted, a bicyclic heterocyclic group which may be substituted, C₂₋₃alkenyl, or C₂₋₃alkynyl;

X is

-   -   (i) a single bond,     -   (ii) C₁₋₆alkylene (for example, C₁₋₅alkylene, C₁₋₄alkylene)         which may be substituted,     -   (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or     -   (iv) C₂₋₄ alkenylene; and

n is an integer selected from 1 to 3.

[Aspect 3] The method according to Aspect 2, wherein

A is C₆₋₁₄aryl (for example, C₆₋₁₃aryl, C₆₋₁₀aryl) which may be substituted;

X is

-   -   (i) a single bond,     -   (ii) C₁₋₅alkylene (for example, C₁₋₅alkylene, C₁₋₄alkylene,         C₁₋₃alkylene) which may be substituted,     -   (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or     -   (iv) C₂₋₃alkenylene; and

n is an integer selected from 1 to 3.

[Aspect 4] The method according to Aspect 2, wherein

A is a bicyclic heterocyclic group which may be substituted;

X is

-   -   (i) a single bond,     -   (ii) C₁₋₆ alkylene (for example, C₁₋₅alkylene, C₁₋₄alkylene,         C₁₋₃alkylene),     -   (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or     -   (iv) C₂₋₃alkenylene; and

n is an integer selected from 1 to 3.

[Aspect 5] The method according to Aspect 2, wherein

A is C₂₋₃ alkenyl; and

X is C₁₋₄alkylene.

[Aspect 6] The method according to Aspect 2, wherein

A is C₂₋₃alkynyl; and

X is C₁₋₄alkylene.

[Aspect 7] The method according to any one of Aspects 1 to 6 and 1-1 to 1-7 wherein the target peptide has 5 to 31 amino acid residues. [Aspect 8] The method according to any one of Aspects 1 to 7 and 1-1 to 1-7 wherein the peptide product comprises an analogue peptide. [Aspect 9] The method according to any one of Aspects 1 to 8 and 1-1 to 1-7 wherein the molar ratio of the analogue peptide to the target peptide is 0.7 or less in the peptide product. [Aspect 10] The method according to any one of Aspects 1 to 9 and 1-1 to 1-7 wherein the peptide synthesis is a solid phase peptide synthesis. [Aspect 11] The method according to any one of Aspects 1 to 10 and 1-1 to 1-7 wherein the target peptide comprises at least one basic amino acid residue and may be free at the N-terminus. [Aspect 12] The method according to any one of Aspects 2, 3, and 7 to 11, wherein

A is C₆₋₁₄aryl (for example, C₆₋₁₃aryl, C₆₋₁₀aryl) which may be substituted with the same or different 1 to 5 substituents selected from the group consisting of C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and C₆₋₁₀aryl.

[Aspect 13] The method according to any one of Aspects 2, 3, and 7 to 12, wherein

A is C₆₋₁₃aryl selected from phenyl, naphthyl, fluorenyl, and indanyl wherein the C₆₋₁₃aryl may be substituted with the same or different 1 to 5 substituents selected from the group consisting of C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and C₆₋₁₀aryl.

[Aspect 13-1] The method according to any one of Aspects 2, 3, and 7 to 12, wherein

A is C₆₋₁₀aryl selected from phenyl, naphthyl, and indanyl wherein the C₆₋₁₀aryl may be substituted with the same or different 1 to 5 substituents selected from the group consisting of C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and C₆₋₁₀aryl.

[Aspect 14] The method according to any one of Aspects 2, 4, and 7 to 11, wherein

A is a bicyclic heterocyclic group selected from the group consisting of 2,3,4,5-tetrahydro-1H-1-benzazepinyl, benzoxanyl, indolinyl, isoindolinyl, phthalazinyl, chromanyl, benzofuranyl, benzothiophenyl, pyrimidinyl, benzothiazolyl, quinolyl, isochromanyl, and benzotriazolyl wherein the bicyclic heterocyclic group may be substituted.

[Aspect 15] The method according to any one of Aspects 2, 4, 7 to 11, and 14, wherein

A is a bicyclic heterocyclic group which may be substituted with the same or different 1 to 5 substituents selected from the group consisting of C₆₋₁₀aryl, C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and oxo.

[Aspect 16] The method according to any one of Aspects 2, 4, 7 to 11, 14 and 15, wherein

A is a bicyclic heterocyclic group selected from

wherein the bicyclic heterocyclic group may be substituted with one phenyl group. [Aspect 17] The method according to any one of Aspects 2 to 4, 7 to 16 and 13-1, wherein X is

-   -   (i) a single bond,     -   (ii) C₁₋₄alkylene (for example, C₁₋₃alkylene) which may be         substituted with the same or different 1 to 3 substituents         selected from the group consisting of methyl, benzyl, cyano, and         phenyl, or     -   (iii) —CO—CH₂— wherein the CO binds to the A.         [Aspect 17-1] The method according to any one of Aspects 2 to 4,         and 7 to 16 and 13-1, wherein X is     -   (i) a single bond,     -   (ii) C₁₋₄alkylene (for example, C₁₋₃alkylene) which may be         substituted with one methyl group, one benzyl group, one cyano         group, and/or one or two phenyl groups, or     -   (iii) —CO—CH₂— wherein the CO binds to the A.         [Aspect 18] The method according to Aspect 12, wherein X is     -   (i) a single bond,     -   (ii) C₁₋₄alkylene (for example, C₁₋₃alkylene) which may be         substituted with the same or different 1 to 3 substituents         selected from the group consisting of methyl, benzyl, cyano, and         phenyl, or     -   (iii) —CO—(CH₂)— wherein the CO binds to the A.         [Aspect 18-1] The method according to Aspect 12, wherein X is     -   (i) a single bond,     -   (ii) C₁₋₄alkylene (for example, C₁₋₃alkylene) which may be         substituted with one methyl group, one benzyl group, one cyano         group, and/or one or two phenyl groups, or     -   (iii) —CO—(CH₂)— wherein the CO binds to the A.         [Aspect 19] The method according to any one of Aspects 2 to 4, 7         to 18, 13-1, 17-1, and 18-1, wherein X is a single bond.         [Aspect 20] The method according to Aspect 16, wherein X is a         single bond.         [Aspect 21] The method according to any one of Aspects 1 to 20,         1-1 to 1-7, 13-1, 17-1, and 18-1, wherein the sulfonic acid         compound is selected from:

[Aspect 22] The method according to any one of Aspects 1 to 21, and 1-1 to 1-7, 13-1, 17-1, and 18-1, further comprising a step of removing the sulfonic acid compound. [Aspect 23] The method according to any one of Aspects 1 to 22, 1-1 to 1-7, 13-1, 17-1, and 18-1, wherein the method is for increasing the molar ratio of the target peptide to an analogue peptide. [Aspect 24] A method for producing a target peptide, comprising the method according to any one of Aspects 1 to 23, 1-1 to 1-7, 13-1, 17-1, and 18-1. [Aspect 25] An agent comprising a target peptide purified by a method comprising the method according to any one of Aspects 1 to 23, 1-1 to 1-7, 13-1, 17-1, and 18-1. [Aspect 26] An agent comprising a sulfonic acid compound for use in the method according to any one of Aspects 1 to 23, 1-1 to 1-7, 13-1, 17-1, and 18-1. [Aspect 27] A compound selected from:

[Aspect 28] An agent comprising a target peptide obtained through purification from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, and the purification comprises steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 28-1] An agent comprising a target peptide obtained through purification from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, and the purification comprises steps:

(1) mixing the peptide product with a sulfonic acid compound in the presence of a solvent;

(2) separating the resulting solid from the liquid phase to collect the resulting solid.

[Aspect 29] An agent comprising a sulfonic acid compound, for use in purification of a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, and the purification comprises steps:

(1) mixing the peptide product with a solvent in the presence of the sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation to collect the solid.

[Aspect 29-1] An agent comprising a sulfonic acid compound, for use in purification of a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, and the purification comprises steps:

(1) mixing the peptide product with the agent comprising the sulfonic acid compound in the presence of a solvent;

(2) separating the resulting solid from the liquid phase to collect the resulting solid.

Effect of the Invention

By the invention of the application, an increased purity of a target peptide is provided from a peptide product obtained through a peptide synthesis, which may comprise an analogue peptide.

DESCRIPTION OF EMBODIMENTS

In one aspect, the present application provides a method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid;

(2) performing a solid-liquid separation to collect the solid.

In one aspect, the present application provides a method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, comprising steps:

(1) mixing the peptide product with a sulfonic acid compound in the presence of a solvent;

(2) separating the resulting solid from the liquid phase to collect the resulting solid.

The term “purify/purification” as used herein means that the purity of a substance is increased. The purity may mean both an absolute purity (the amount of a substance of interest relative to the total amount of the mixture comprising the substance of interest) and a relative purity (the amount of a substance of interest relative to the amount of another substance (for example, impurity), in a mixture).

For example, in the present invention, the term “purifying a target peptide” includes a case where the amount of the target peptide in the solid obtained after mixing with the sulfonic acid compound relative to the weight obtained by subtracting the portion corresponding to the sulfonic acid compound from the solid obtained after mixing with the sulfonic acid compound is increased as compared to the amount of the target peptide relative to the total amount of the peptide product before mixing with the sulfonic acid compound (for example, increase in % by weight). In the present invention, the term “purifying a target peptide” includes, for example, a case where the molar ratio of the target peptide to the analogue peptide in the resulting solid after the mixing with sulfonic acid compound is increased as compared with before the mixing.

In the present application, the method for determining the purity of the target peptide is not particularly limited, and the purity may be determined by a commonly used method (for example, HPLC method).

In the present application, the term “peptide synthesis” is not particularly limited as long as it is a method for synthesizing a peptide, and examples thereof include an organic chemical synthesis method (for example, solid phase and liquid phase methods) and fermentation methods, which may be performed by a commonly used method. In peptide synthesis, the synthesis conditions (for example, resin, protecting group, reaction temperature, reaction time, and solvent in the organic chemical synthesis methods; culture conditions, host, vector, nucleic acid sequence in the fermentation methods) are usually set so as to suppress the generation of impurities (for example, analogue peptide(s)). Also in the present application, the peptide synthesis is preferably conducted under synthesis conditions in which generation of analogue peptide(s) is suppressed, on the basis of the knowledge generally known to a person skilled in the art, and the amount of substance of the target peptide is preferably larger than that of the analogue peptide, in the peptide product obtained through the peptide synthesis.

For example, in the peptide product obtained through peptide synthesis, the molar ratio of the analogue peptide to the target peptide (analogue peptide/target peptide) is 0.7 or less (preferably 0.6 or less, more preferably 0.5 or less, still more preferably 0.45 or less, still more preferably 0.4 or less, and more preferably 0.2 or less). A lower molar ratio of the analogue peptide to the target peptide is preferable. Thus the lower limit of the range of the molar ratio is not particularly limited, but examples of the range of the molar ratio include 0.0001 to 0.7, 0.001 to 0.6, and 0.01 to 0.5. For example, an approximate value of the molar ratio (for example, area ratio) calculated based on a value obtained by HPLC may be used as the molar ratio.

In a peptide product obtained through a peptide synthesis, “the amount of substance of the target peptide is larger than that of the analogue peptide” means that the amount of substance of the target peptide is larger than the amount of substance of one kind of analogue peptide, and when a multiple kinds of analogue peptides are comprised, it means that the amount of substance of the target peptide is larger than that of each analogue peptide. In a peptide product obtained through a peptide synthesis, “the amount of substance of the target peptide is larger than that of the analogue peptide” may be indicated by the extremely high probability that in the peptide product the amount of substance of the analogue peptide is lower than that of the target peptide due to the fact that the amount of the target peptide relative to the total amount of the peptide product obtained through a peptide synthesis, the absolute purity, is large (for example, the concentration of the target peptide in the peptide product is 40 wt. % or more, 50 wt. % or more, 60 wt. % or more, 70 wt. % or more, 80 wt. % or more, or 90 wt. % or more).

In the present application, “target peptide” means a peptide which is produced by a peptide synthesis carried out for the purpose of producing the peptide. The structure of the target peptide is not particularly limited so long as: is free at the N-terminus; has at least 1 (for example, 1 to 5, 1 to 4, 1 to 3, 1 to 2, and 1) basic amino acid residue; or the N-terminus is free and has at least 1 (for example, 1 to 5, 1 to 4, 1 to 3, 1 to 2, and 1) basic amino acid residue. The target peptide preferably has 5 to 31 amino acid residues, more preferably 5 to 25, still more preferably 5 to 20, and even more preferably 5 to 15 amino acid residues. The range of the number of amino acid residues of the target peptide may also be indicated by a combination of a lower limit selected from 5, 6, 7, and 8 and an upper limit selected from 31, 25, 20, 15, and 10.

The amino acid residues which may be comprised in the target peptide may be those derived from naturally occurring amino acids such as L-selenocysteine, 2-aminoisobutyric acid, D-isovaline, L-isovaline, L-norleucine, and L-ornithine in addition to the 20 amino acids listed in the table below (L-form except glycine, which does not have an asymmetric carbon) which usually constitute a protein; and those derived from unnatural amino acids which do not exist in nature or exist in small amounts, if any (therefore, it is usually produced by chemical synthesis, etc.).

Examples of unnatural amino acids include:

-   D forms of the 19 amino acids, excluding glycine, shown in the table     below; -   N-methylated forms of the 20 amino acids shown in the table below     (for example, N-methylglycine, L-N-methylphenylalanine) and     enantiomers of L-N-methylated forms of the 19 amino acids, excluding     N-methylglycine, shown in the table below; -   both enantiomers of α-methylated forms of the 18 amino acids,     excluding glycine and alanine, shown in the table below (for     example, α-methyllysine); -   both enantiomers of α-ethylated forms of the 19 amino acids,     excluding alanine, shown in the table below; -   D-selenocysteine; -   D-norleucine; -   D-ornithine; -   (S)- or (R)-2,3-diaminopropionic acid; -   (S)- or (R)-2,4-diaminobutyric acid; -   (S)- or (R)-pyroglutamic acid; -   (S)- or (R)-α-methyl-orthofluorophenylalanine; -   (S)- or (R)-α-(4-pentenyl)alanine; -   (S)- or (R)-α-(7-octenyl)alanine; -   (S)- or (R)-α-propargylalanine; -   (S)- or (R)-α-allylalanine; -   (S)- or (R)-indan-2-ylglycine; -   (S)- or (R)-pyridin-3-ylmethylglycine, and derivatives thereof in     which the pyridine ring may be substituted with phenyl group(s)     which may be substituted with alkyl group(s); -   (S)- or (R)-pyridin-2-ylmethylglycine; -   (S)- or (R)-pipecolic acid; and -   (S)- or (R)- and trans- or cis-4-hydroxyproline; -   RC8 ((R)-α-(7-octenyl)alanine); -   SC5 ((S)-α-(4-pentenyl)alanine).

alanine A leucine L arginine R lysine K asparagine N methionine M aspartic acid D phenylalanine F cysteine C proline P glutamine Q serine S glutamic acid E threonine T glycine G tryptophan W histidine H tyrosine Y isoleucine I valine V

In the present application, the term “basic amino acid residue” means an amino acid residue derived from an amino acid having basic moiety (moieties) other than the amino group (for example, D- or L-lysine, D- or L-arginine, D- or L-histidine, D- or L-ornithine, (S)- or (R)-2,3-diaminopropionic acid, and (S)- or (R)-2,4-diaminobutyric acid).

In the present application, the target peptide may be modified at the terminus (termini) with a protecting group and the like commonly used in peptide synthesis. For example, the N-terminus may be modified with Ac group (acetyl group), Fmoc group (9-fluorenylmethyloxycarbonyl group), or Boc group (tert-butoxycarbonyl group). For example, the C-terminus may be modified with an amide group or an ester group.

In the present application, the term “analogue peptide” refers to a peptide that may be produced by peptide synthesis for producing a target peptide and that is not the target peptide. Examples of the analogue peptide include peptide(s) in which:

(1) some of the amino acid residues (for example, continuous or discontinuous 1 to 3 amino acid residues, continuous or discontinuous 1 to 2 amino acid residues, or amino acid residue) in the target peptide are/is duplicated; (2) some of the amino acid residues (for example, continuous or discontinuous 1 to 3 amino acid residues, continuous or discontinuous 1 to 2 amino acid residues, or 1 amino acid residue) in the target peptide are/is deleted. (3) some of the amino acid residues (for example, continuous or discontinuous 1 to 3 amino acid residues, continuous or discontinuous 1 to 2 amino acid residues, or amino acid residue) in the target peptide are/is epimerized (for example, epimerization by isomerization at α-position of N-protected amino acid); and/or (4) some of the amino acid residues (for example, continuous or discontinuous 1 to 3 amino acid residues, continuous or discontinuous 1 to 2 amino acid residues, and 1 amino acid residue) in the target peptide are/is replaced by the same number of amino acid residue(s).

The number of amino acid residues of the analogue peptide is, for example, the same as, 1 to 3 (preferably 1 to 2, more preferably 1) more than, or 1 to 3 (preferably 1 to 2, more preferably 1) less than the number of amino acid residues of the target peptide.

The “analogue peptide” may have basic moiety/moieties (for example, is free at the N-terminus/has at least 1 (for example, 1 to 5, 1 to 4, 1 to 3, 1 to 2, or 1) basic amino acid residue), or may not have such a basic moiety. As described above, in a peptide product obtained through a peptide synthesis, the amount (amount of substance) of a target peptide is usually larger than that of analogue peptide, and when the structures of the target peptide and the analogue peptide are similar, the solubility properties of the target peptide and the analogue peptide in a solvent may usually be similar. Therefore, in the solid obtained after mixing with the sulphonic acid compound, the ratio of the target peptide, which was originally contained more than the analogue peptide, may be increased although when the “analogue peptide” has a basic moiety, a solid may be formed by forming a salt with the sulphonic acid compound. However, the effect of the present invention is not limited to any specific mechanism.

In the present application, a solvent used in mixing with a sulfonic acid compound is not particularly limited, and may be appropriately selected in consideration of the purification efficiency of the target peptide. Examples of the solvent include:

water;

alcohol compounds (for example, C₁₋₄ alcohol (for example, isopropyl alcohol, methanol, ethanol));

acetonitrile;

ether compounds (for example, C₂₋₆ ether (for example, diethyl ether, MTBE, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, and CPME (cyclopentyl methyl ether)));

ketone compounds (for example, C₃₋₆ ketone (for example, acetone), MEK (methyl ethyl ketone), methyl isopropyl ketone, MIBK (methyl isobutyl ketone));

ester compounds (for example, C₃-6 ester (for example ethyl acetate, isopropyl acetate, t-butyl acetate));

hydrocarbon compounds (for example, 06-9 hydrocarbon (for example, toluene));

DMSO;

amide compounds (for example, DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide), NMP (N-methylpyrrolidone));

halogenated hydrocarbons (for example, chloroform, dichloromethane, 1,2-dichloroethane); and

mixture thereof (wherein the mixture means any combination thereof). The solvent may further contain other substance(s).

Further examples of the solvent include water, isopropyl alcohol (IPA), methanol (MeOH), 1,4-dioxane, 1,2-dimethoxyethane (DME), tetrahydrofuran (THF), acetone, acetonitrile, ethanol, ethyl acetate, toluene, MTBE, DMSO, diethyl ether, and a mixture thereof (where the mixture means any combination thereof). The solvent may further contain other substance(s).

When a peptide product obtained through a peptide synthesis is mixed with a sulfonic acid compound in the presence of a solvent, the amounts of the solvent and the sulfonic acid compound(s) relative to the peptide product are not particularly limited and may be appropriately selected in consideration of the purification efficiency of the target peptide. The solvent may be used at the weight-by-weight ratio to the target peptide obtained by peptide synthesis in the range of 1 to 100000, preferably 1 to 10000, preferably 1 to 2000, and more preferably 10 to 1000, which may be based on the theoretical value of the weight of the target peptide.

For example, the molar ratio of the sulfonic acid compound to the target peptide may be in the range 0.1 to 50, preferably 0.2 to 40, more preferably 0.3 to 30, and even more preferably 0.5 to 20, which may be based on the theoretical value of the amount of substance of the target peptide.

Further, the sulphonic acid compound may be used at the molar ratio to the target peptide, which may be based on the theoretical value of the amount of substance of the target peptide, in the ranges:

when the sulfonic acid compound has one sulfo group, for example, in the range 0.5 to 20, preferably 0.8 to 10, more preferably 1 to 8, even more preferably 1.5 to 7;

when the sulfonic acid compound has 2 sulfo groups, for example, in the range 0.2 to 10, preferably 0.4 to 5, more preferably 0.5 to 4, even more preferably 0.75 to 3.5;

when the sulfonic acid compound has 3 sulfo groups, for example, in the range 0.15 to 6, preferably 0.3 to 3.3, more preferably 0.4 to 2.6, and even more preferably 0.5 to 2.3.

The theoretical value may mean a value calculated by assuming that the purity of the target peptide in the peptide synthesis product is 100%.

The method for separating the resulting solid from the liquid phase to collect the resulting solid (solid-liquid separation) after mixing with the sulfonic acid compound is not particularly limited, and may be appropriately selected depending on the production scale, etc., and for example, includes filtration, centrifugation, decant, etc.

Since the purity of the target peptide in the solid may be increased through solid-liquid equilibrium, the solid-liquid separation is preferably performed after a predetermined time (for example, 1 minute or more, 2 minutes or more, 3 minutes or more, 4 minutes or more, 5 minutes or more, 10 minutes or more, 30 minutes or more, 1 hour or more, 2 hours or more, 3 hours or more) has elapsed after the mixing the peptide product with the sulfonic acid compound and the solvent.

In consideration of operation efficiency, it is preferable that the solid-liquid separation is performed, for example, within one day, within two days, within one week, or within two weeks, but the mixture may be stored without the solid-liquid separation, and then the solid-liquid separation may be performed accordingly.

The temperature at the time of mixing with the sulfonic acid compound and/or the solvent and at the time of separating the resulting solid from the liquid phase to collect the resulting solid (solid-liquid separation) is not particularly limited, and may be appropriately selected in consideration of the purification efficiency of the target peptide, for example. The examples include 0 to 50° C., 0 to 40° C., 0 to 30° C., and 10 to 25° C.

The solid obtained by the solid-liquid separation may be optionally washed. The liquid used for washing (the liquid for washing) is not particularly limited, and may be appropriately selected in consideration of the purification efficiency of the target peptide. Examples of the liquid for washing include:

water;

alcohol compounds (for example, C₁₋₄alcohol (for example, isopropyl alcohol, methanol, ethanol));

acetonitrile;

ether compounds (for example, C₂₋₆ ether (for example, diethyl ether, MTBE, tetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, CPME (cyclopentyl methyl ether)));

ketone compounds (for example, 03-6 ketone (for example, acetone), MEK (methyl ethyl ketone), methyl isopropyl ketone, MIBK (methyl isobutyl ketone));

ester compounds (for example, C₃₋₆ester (for example, ethyl acetate, isopropyl acetate, t-butyl acetate));

hydrocarbon compounds (for example, 06-9hydrocarbon (for example, toluene));

DMSO;

amide compounds (for example, DMF (N,N-dimethylformamide), DMA (N,N-dimethylacetamide), NMP (N-methylpyrrolidone));

halogenated hydrocarbons (for example, chloroform, dichloromethane, 1,2-dichloroethane); and

mixture thereof (wherein the mixture means any combination thereof). The liquid for washing may further contain other substance(s).

Repeating the purification method of the present application on the solid obtained by the purification method of the present application is one embodiment of the purification method of the present application. The purity of the target peptide may be increased by repeating the purification method of the present application.

The purification method of the present application may be performed in combination with other purification method(s) (for example, preparative HPLC, recrystallization, dispersion and wash). For example, the solid obtained by the method of the present application may be subjected to another purification method, or a peptide product previously purified by another purification method may be subjected to the purification method of the present invention.

It is preferable that the sulfonic acid compound is removed from the solid obtained by the purification method of the present application in a further purification step. The method for removing the sulfonic acid compound is not particularly limited, and may be carried out by a usual method for removing the sulfonic acid compound (for example, an acid or alkali treatment, and a removal method using an ion exchange resin).

In the present application, the term “sulfonic acid compound” means an organic compound having sulfo group(s) (—SO₃H). In the present application, the sulfonic acid compound is preferably those where a sulfo group is attached to a moiety having one or more unsaturated bonds through a single bond or a short linker (for example, C₁₋₁₂, C₁₋₆, C₁₋₄, etc.).

Preferred examples of the sulfonic acid compound include a sulfonic acid compound of formula (I):

wherein:

A is C₆₋₁₄aryl (for example, C₆₋₁₃aryl, C₆₋₁₀aryl) which may be substituted, a bicyclic heterocyclic group which may be substituted, C₂₋₃alkenyl, or C₂₋₃alkynyl;

X is

-   -   (i) a single bond,     -   (ii) C₁₋₆alkylene (for example, C₁₋₅ alkylene, C₁₋₄alkylene)         which may be substituted,     -   (iii) —CO—(CH₂)_(n)-wherein the CO binds to the A, or (iv)         C₂₋₄alkenylene; and n is an integer selected from 1 to 3.

The term “C₆₋₁₄aryl” as used herein alone or as part of another group refers to a 6 to 14 membered monocyclic, bicyclic or tricyclic aromatic hydrocarbon ring group and a ring group wherein one cycloalkane is fused to said aromatic hydrocarbon ring. Examples of C₆₋₁₄aryl include phenyl, naphthyl, indanyl, tetrahydronaphthyl, and fluorenyl.

The term “C₆₋₁₀ aryl” as used herein alone or as part of another group refers to a 6 to 10 membered monocyclic or bicyclic aromatic hydrocarbon ring group, and a ring group wherein one cycloalkane is fused to said aromatic hydrocarbon ring group. Examples of C₆₋₁₀ aryl include phenyl, naphthyl, indanyl, and tetrahydronaphthyl.

Examples of “C₆₋₁₄aryl (or C₆₋₁₃aryl, C₆₋₁₀aryl) which may be substituted” include C₆₋₁₄ aryl (or C₆₋₁₃ aryl, C₆₋₁₀ aryl) which may be substituted with the same or different 1 to 5 (for example, 1 to 3, 1 to 2, and 1) substituents selected from the group consisting of C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and C₆₋₁₀aryl.

The term “a bicyclic heterocyclic group” as used herein means a 8 to 11 membered bicyclic group wherein a monocyclic aromatic ring having 1 to 4 heteroatoms selected from a nitrogen atom, an oxygen atom and a sulfur atom (for example, pyridine, furan, thiophene, imidazole, pyrimidine, oxazole, thiazole, thiazine, triazole) or a monocyclic non-aromatic ring (tetrahydropyran, azepane, piperidine, etc.) is fused to a monocyclic aromatic ring (benzene, pyridine, etc.). The bicyclic heterocyclic group may be attached to another moiety at any heteroatom or carbon atom which results in a stable structure. The bicyclic heterocyclic group may comprise one or more (for example, 1 or 2) oxo groups. Examples of the bicyclic heterocyclic group include:

2,3,4,5-tetrahydro-1H-1-benzazepinyl, benzoxanyl, indolinyl, isoindolinyl, phthalazinyl, chromanyl, benzofuranyl, benzothiophenyl, pyrimidinyl, benzothiazolyl, quinolyl, isochromanyl, and benzotriazolyl.

Examples of “a bicyclic heterocyclic group which may be substituted” as used herein include a bicyclic heterocyclic group which may be substituted with the same or different 1 to 5 (for example, 1 to 3, 1 to 2, and 1) substituents selected from the group consisting of C₆₋₁₀aryl, C₁₋₄alkyl, —CO—C₆₋₁₀aryl, —OH, —O—C₁₋₃alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄alkyl, —CF₃, and oxo.

As used herein, “02-3alkenyl” means a straight or branched unsaturated hydrocarbon group having 2 to 3 carbon atoms and comprising 1 or 2 double bonds, examples of which include vinyl, allyl, 1-propenyl, isopropenyl, allenyl.

As used herein, “02-3alkynyl” means a straight or branched unsaturated hydrocarbon group having 2 to 3 carbon atoms and comprising one triple bond, examples of which include ethynyl, propynyl (1-propynyl, 2-propynyl).

As used herein, “C₁₋₄alkylene” means a divalent group derived from a straight chain C₁₋₄alkyl. Examples of C₁₋₄alkylene include methylene, ethylene, trimethylene, and tetramethylene.

As used herein, “C₁₋₆alkylene” means a divalent group derived from a straight chain C₁₋₆alkyl. Examples of C₁₋₆alkylene include methylene, ethylene, trimethylene, tetramethylene, and pentamethylene.

As used herein, “C₁₋₃alkylene” means a divalent group derived from a straight chain C₁₋₃alkyl. Examples of C₁₋₃alkylene include methylene, ethylene, and trimethylene.

As used herein, examples of “C₁₋₆alkylene (or C₁₋₅alkylene, C₁₋₄alkylene, C₁₋₃ alkylene) which may be substituted” include C₁₋₆alkylene (or C₁₋₅alkylene, C₁₋₄alkylene, C₁₋₃alkylene) which may be substituted with the same or different 1 to 3 substituents selected from the group consisting of methyl, benzyl, cyano, and phenyl (for example, C₁₋₆alkylene (or C₁₋₅alkylene, C₁₋₄alkylene, C₁₋₃alkylene) which may be substituted with one methyl group, one benzyl group, or one phenyl group)).

In the “—CO—(CH₂)_(n)—” as used herein, n is an integer of 1 to 3 (preferably 1 to 2), and preferred examples of —CO—(CH₂)_(n)— include —CO—CH₂—.

As used herein, “C₂₋₄alkenylene” means a divalent group derived from a straight chain C₂₋₄alkenyl. As used herein, “C₂₋₃alkenylene” means a divalent group derived from a straight chain C₂₋₃alkenyl. Examples of C₂₋₄alkenylene and C₂₋₃alkenylene include vinylene(—CH═CH—), and propenylene(—CH₂CH═CH—).

The term “C₁₋₄alkyl” as used herein alone or as part of another group means a straight or branched saturated hydrocarbon group having 1 to 4 carbon atoms. Examples of C₁₋₄alkyl include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, and tert-butyl.

The term “C₁₋₃alkyl” as used herein alone or as part of another group means a straight or branched saturated hydrocarbon group having 1 to 3 carbon atoms. Examples of C₁₋₃alkyl include methyl, ethyl, propyl, and isopropyl.

As used herein, examples of a “—CO—C₆₋₁₀aryl” include —CO-phenyl.

As used herein, examples of the halogen include fluorine (F), chlorine (Cl), bromine (Br) and iodine (I).

More preferred examples of the sulfonic acid compound include those listed in [Aspect 21] above.

One aspect of the present invention provides a method for producing a target peptide comprising the purification method of the present application.

One aspect of the present invention provides an agent comprising a target peptide purified by a method comprising the purification method of the present application. The agent may be prepared by a usual method.

One aspect of the present invention provides an agent comprising a sulfonic acid compound for use in the purification method of the present application. The agent may be prepared by a usual method.

EXAMPLE

The present invention is explained in further detail with reference to Test examples. However, the scope of the invention is not limited to these Examples.

Purification of Target Peptide Outline of Examinations:

When a target peptide is synthesized by solid phase method, it is expected that analogue peptides are contained in the resulting crude peptide as impurities, but it is difficult to identify what kind of analogue peptides are actually contained. Therefore, the target peptide and the pseudo-analogue peptide having a known sequence as the analogue peptide are synthesized by solid phase method, and the resulting crude target peptide, the resulting crude pseudo-analogue peptide, and each acid compound are dissolved in a solvent, which provides a uniform sample to obtain a value before the treatment by HPLC, followed by lyophilization to remove the solvent. A solvent is added to the residue to provide a solid-liquid mixture, and then the supernatant is removed. The ratio of the amount of substance (mol) of the target peptide in the solid to the sum of the amount of substance (mol) of the target peptide and the amount of substance (mol) of the pseudo-analogue peptide in the solid is determined. Whether the target peptide is purified in the solid is evaluated by the change of the ratios.

1-1: Synthesis of Peptide

The target peptides and the analogue peptides (pseudo) shown in the tables below were respectively synthesized by the solid phase method described below.

TABLE 1-1 Target peptide Analogue peptide  (1) Ac—YFYPEL—NH₂ (SEQ ID NO: 1)  (1) Ac—YYPEL—NH₂ (SEQ ID NO: 16) (27) Ac—YHYPEL—NH₂ (SEQ ID NO: 62)  (2) H—YYPEL—NH₂ (SEQ ID NO: 17) (28) Ac—Y(MeK)YPEL—NH₂ (SEQ ID NO: 63)  (3) H—VIRALRALVALRALR—OH (SEQ ID NO: 18)  (2) H—YFYPEL—NH₂ (SEQ ID NO: 2)  (4) H—ARLDVASEFRKKNKALSR—NH₂  (SEQ ID NO: 19)   (3) H—VIRALRRALVALRALR—OH (SEQ ID NO: 3)  (5) H—HAEGTFTSDVSSYLEGQAAKEFAWLVKGRG—OH (SEQ ID NO: 20)   (4) H—ARLDVASEFRKKWNKALSR—NH₂   (6) H—AGCKNFFWKTFTSC—OH (SEQ ID NO: 21) (SEQ ID NO: 4)  (5) H—HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG—OH (35) H—AGcKNFFWKTFTSC—OH (SEQ ID NO: 5)  (6) H—AGCKNFFWKTFTS—OH (SEQ ID NO: 6)  (7) H—AQKLRAD—OH (SEQ ID NO: 22)  (7) H—AQKLRASD—OH (SEQ ID NO: 7)  (8) H—AKLRAD—OH (SEQ ID NO: 23)  (8) H—YERAKSNM—OH (SEQ ID NO: 8) (19) H—QKLRASD—OH (SEQ ID NO: 24) (20) H—AQKLRSD—OH (SEQ ID NO: 25) (21) H—AQKLRAS—OH (SEQ ID NO: 26) (24) H—AQKRASD—OH (SEQ ID NO: 27) (27) H—AQKLASD—OH (SEQ ID NO: 28)  (9) H—YERAKNM—OH (SEQ ID NO: 29) (13) H—YERKSNM—OH (SEQ ID NO: 30) (14) H—YERASNM—OH (SEQ ID NO: 31) (16) H—YERAKSM—OH (SEQ ID NO: 32) (22) H—ERAKSNM—OH (SEQ ID NO: 33) (23) H—YERAKSN—OH (SEQ ID NO: 34) (28) H—YRAKSNM—OH (SEQ ID NO: 35)

TABLE 1-2 Target peptide Analogue peptide  (9) H—FRVDEEFQSPFASQSRGYFLFRPRN—NH₂  (10) H—FRVDEEFQSPFASQSRGYFLFRRN—NH₂  (SEQ ID NO: 9) (SEQ ID NO: 36) (11) H—GGGRG—NH₂ (SEQ ID NO: 10)  (11) H—GGGG—NH₂ (SEQ ID NO: 37) (12) Ac—ALRAL—NH₂ (SEQ ID NO: 11)  (12) Ac—ALAL—NH₂ (SEQ ID NO: 38) (13) Ac—ALRAL—OH (SEQ ID NO: 12)  (15) Ac—ALAL—OH (SEQ ID NO: 39) (14) H—ALRALRALR—OH (SEQ ID NO: 13)  (17) H—ALALRALR—OH (SEQ ID NO: 40) (15) Ac—GGRGG—NH₂ (SEQ ID NO: 14)  (18) Ac—GGGG—NH₂ (SEQ ID NO: 41) (16) H—HSDGTFTSELSRLREGARLQRLLQGLV—NH₂ (30) H—HSDGTFTSELSRLEGARLQRLLQGLV—NH₂ (SEQ ID NO: 15) (SEQ ID NO: 42) (17) Pyr—HWSYlLRP—NH₂ (26) Pyr—HWSYLLRP—NH₂ (SEQ ID NO: 43) (18) H—HVTTV—NH₂ (SEQ ID NO: 44) (31) Pyr—HWSYlLLRP—NH₂ (19) H—YERAKSNM—NH₂ (SEQ ID NO: 46) (32) H—VTTV—NH₂ (SEQ ID NO: 45) (20) H—VKRESYSGVT—NH₂ (SEQ ID NO: 48) (33) H—hVTTV—NH₂ (21) H—RAVLP—OH (SEQ ID NO: 49) (34) H—YERAKSNL—NH₂ (SEQ ID NO: 47) (22) H—(RC8)RRR((Me)F)R(SC5)—NH₂ (36) H—VKRESYSGV—NH₂ (SEQ ID NO: 55) (SEQ ID NO: 50) (23) Ac—HYFYPEL—NH₂ (SEQ ID NO: 51) (37) H—RALP—OH (SEQ ID NO: 56)  (24) H—WPVTLNAQTID—NH₂ (SEQ ID NO: 52) (38) H—(RC8)RRRR(SC5)—NH₂  (SEQ ID NO: 57) (25) H—T((Me)G)RK(Dap)H—OH  (39) Ac—HYYPEL—NH₂ (SEQ ID NO: 58)  (SEQ ID NO: 53) (26) Pyr—GPWLEEEEEAYGWMDF—NH₂  (40) H—PVTLNAQTID—NH₂ (SEQ ID NO: 59) (SEQ ID NO: 54) (41) H—((Me)G)RK(Dap)H—OH  (SEQ ID NO: 60) (42) Pyr—GPWLEEEEEYGWMDF—NH₂  (SEQ ID NO: 61)

The apparatus used in Test examples are as follows.

Peptide synthesizer: “KMS-3” (KOKUSAN CHEMICAL Co., Ltd.).

Mass spectrometer: “6224 TOF LC/MS” and “1260 Infinity series” (Agilent). Ionization condition: ESI (capillary voltage: 3500 V, Fragmentor voltage: 100 V).

HPLC analyzer: “SPD-M20A”, “LC-20AD”, “SIL-20AC”, “DGU-20A”, “CTO-20AC”, “CBM-20A” (Shimadzu); or “SPD-M20A”, “LC-2010C” (Shimadzu); or “1200 series” (Agilent).

(1) Synthesis of Protected Peptide Resin

In syntheses of protected peptide resins, the α-amino group of each constituent amino acid was all protected with a 9-fluorenylmethyloxycarbonyl group (Fmoc group).

Regarding active side chains, the β-carboxyl group of aspartic acid and the γ-carboxyl group of glutamic acid was protected with a tert-butyl group (tBu group); the guanidino group of arginine was protected with a 2,2,4,6,7-pentamethyl-2,3-dihydrobenzofuran-5-ylsulfonyl group (Pbf group); the hydroxyl group of serine and threonine was protected with a tert-butyl group (tBu group); the thiol group of cysteine and the imidazole group of histidine was protected with a trityl group (Trt group); the phenolic hydroxyl group of tyrosine was protected with a tert-butyl group (tBu group); the carboxamide group of asparagine and glutamine was protected with a trityl group (Trt group); the ε-amino group of lysine, the β-amino group of Dap and the indole group of tryptophan were protected with a tert-butyloxycarbonyl group (Boc group).

Regarding resins, (2-chloro)trityl chloride resin (WATANABE CHEMICAL INDUSTRIES, LTD., approx. 1.6 mmol/g) was used for synthesizing a peptide sequence having a C-terminal carboxylic acid; and Fmoc-NH-SAL resin (WATANABE CHEMICAL INDUSTRIES, LTD., approx. 0.43 mmol/g) was used for synthesizing a peptide sequence having a C-terminal carboxamide. In the case of synthesizing the peptide sequence having the C-terminal carboxylic acid, in order to introduce the C-terminal amino acid, a solution of Fmoc amino acid (2.5 equivalents relative to the resin) in DMF, and N,N-diisopropylethylamine (2.5 equivalents relative to the resin) were added to the resin, followed by shaking and stirring for 2 hours or longer. In the case of synthesizing the peptide sequence having the C-terminal carboxamide, to remove the Fmoc group from the resin, a solution of 20% piperidine in DMF was added to the resin, followed by shaking and stirring for not less than 10 minutes and washing the resin 3 to 5 times with DMF, and then to introduce the C-terminal amino acid, a solution of Fmoc amino acid (2.5 equivalents relative to the resin) in DMF, a solution of 1-hydroxybenzotriazole (2.5 equivalents relative to the resin) in DMF, and DIC (2.5 equivalents relative to the resin) were added thereto, followed by shaking and stirring for not less than 40 minutes.

After the C-terminal amino acid was introduced to the resin, the excess amounts of reagents were removed by washing the resin 3 to 5 times with DMF, and then the Fmoc group, the protecting group of the terminal amino group, was removed by shaking and stirring with 20% piperidine at room temperature for 10 minutes or more. The piperidine was removed by washing the resin with DMF 3 to 5 times and then a condensation with the carboxyl group of the Fmoc-protected derivative of the next amino acid in the amino acid sequence of the peptide to be produced was performed. The condensation was performed by adding a solution of the Fmoc-amino acid (2.5 equivalents relative to the resin) in DMF, a solution of 1-hydroxybenztriazole (2.5 equivalents relative to the resin) in DMF, and DIC (2.5 equivalents relative to the resin). Removals of Fmoc group and condensation reactions with Fmoc amino acid were repeated in a similar way until the amino acid sequence of the peptide to be produced was formed to synthesize the protected peptide resin with amino acid sequence of the peptide to be produced.

In a case of synthesizing a peptide having a free amino group at the N-terminus, after the condensation of the Fmoc amino acid of the N-terminus, the Fmoc group was removed by shaking and stirring in a solution of 20% piperidine in DMF at room temperature for 10 minutes or more, and then the piperidine was removed by washing the resin 3 to 5 times with DMF to complete the synthesis of the protected peptide resin. In a case of synthesizing a peptide sequence whose N-terminus was protected by an Ac group, after the N-terminus was converted to a free amino group as described above, a condensation reaction was performed by adding acetic acid (5 equivalents), a solution of N-hydroxysuccinic acid (4.95 equivalents) in DMF, and DIC (5 equivalents) to introduce an Ac group to the N-terminus to synthesize the protected peptide resin having the amino acid sequence of the peptide to be produced. When the N-terminal amino acid residue was (S)- or (R)-pyroglutamic acid, a condensation reaction was carried out by shaking and stirring with (S)- or (R)-Fmoc-pyroglutamic acid chloride (5 equivalents) corresponding to the N-terminal Fmoc amino acid and pyridine (10 equivalents) for at least 40 minutes, and then the Fmoc group was removed by shaking and stirring with a solution of 20% piperidine in DMF for at least 10 minutes at room temperature, and then the piperidine was removed by washing the resin 3 to 5 times with DMF to complete the synthesis of the protected peptide resin.

(2) Synthesis of Crude Peptide Product

In a synthesis of the crude peptide product, the above protected peptide resin having the amino acid sequence of the peptide to be produced was subjected to deprotection and excision from the resin by treating with an acid. When the peptide to be produced had a peptide sequence comprising an amino acid(s) having a sulfur atom, such as cysteine or methionine, the deprotection and excision from the resin were performed by shaking and stirring with TFA/water/ethanedithiol/TIS (94/2.5/2.5/1) for 30 minutes or more at a temperature from cooling with ice to room temperature. When the peptide to be produced had a peptide sequence not comprising an amino acid having a sulfur atom, such as cysteine or methionine, the deprotection and excision from the resin were performed by shaking and stirring with TFA/water/TIS (95/2.5/2.5) for 30 minutes or more at a temperature from cooling with ice to room temperature. After the completion of the reaction, the resin was removed by filtration and washed 3 to 5 times with the solution for deprotection, and the filtrate combined with the washings was concentrated by an evaporator. MTBE was added to the residue, and the resulting precipitates were subjected to a solid-liquid separation by filtration or centrifugation, followed by multiple washes with MTBE to provide the crude peptide product of interest.

Method for Producing (8) H-YERAKSNM-OH (Method A)

(1) To a column made of PP, attached to the peptide synthesizer “KMS-3” was added 187.5 mg (0.30 mmol) of (2-chloro) trityl chloride resin (WATANABE CHEMICAL INDUSTRIES, LTD., approx. 1.6 mmol/g). Five milliliters of DMF was added thereto, and the mixture was shaken and stirred overnight. After removal of the DMF by suction filtration, to the residue were added 2 mL of a solution of Fmoc-Met-OH in DMF (375 mM) (0.75 mmol; 2.5 equivalents), 128 μL of N,N-diisopropylethylamine (0.75 mmol; 2.5 equivalents), and 1 mL of DMF. The resulting mixture was shaken and stirred for 6 hours. After removal of the liquid by suction filtration, the residue was washed with 3 mL of DMF (5 times). To the residue was added 3 mL of a solution of 20% piperidine in DMF, and the mixture was shaken and stirred for 35 minutes. The reaction mixture was filtered by suction, and the residue was washed 5 times with 3 mL of DMF. (2) To the residue were added 2 mL of a solution of Fmoc-Asn(Trt)-OH in DMF (375 mM) (0.75 mmol; 2.5 equivalents), 1 mL of a solution of 1-hydroxybenzotriazole in DMF (750 mM) (0.75 mmol; 2.5 equivalents), and 116 μL of DIC (0.75 mmol; 2.5 equivalents), and then the mixture was shaken and stirred overnight. After removal of the liquid by suction filtration, the residue was washed 5 times with 3 mL of DMF. To the residue was added 3 mL of a solution of 20% piperidine in DMF, and the mixture was shaken and stirred for 35 minutes. The mixture was filtered by suction, and the residue was washed 5 times with 3 mL of DMF. (3) With Reference to the step (2) above, the subsequent amino acids were sequentially combined. The order and reaction time of the subsequent amino acids were Fmoc-Ser(tBu)-OH 20 h, Fmoc-Lys(Boc)-OH 45 min, Fmoc-Ala-OH 3 h, Fmoc-Arg(Pbf)-OH 16 h, Fmoc-Glu(tBu)-OH 2.5 h, and Fmoc-Tyr(tBu)-OH 15 h. (4) To the resulting protected peptide resin was added 3 mL of a solution for deprotection (TFA/water/ethanedithiol/TIS=94/2.5/2.5/1) under ice cooling, and the ice bath was removed and the mixture was shaken and stirred at ambient temperature for 3 hours. The resin was filtered off and washed three times with the solution for deprotection. The filtrate combined with the washings was concentrated by an evaporator. To the residue was added 5 mL of MTBE, and the mixture was stirred overnight under ice cooling. The entire amount of the mixture was transferred to a centrifuge tube, and centrifuged at 3000 rpm for 1 minute, and then the supernatant was removed. To the precipitate was added 2 mL of MTBE, and the mixture was shaken and stirred for 3 minutes, centrifuged at 3000 rpm for 1 minute, and then the supernatant was removed, which was repeated 3 times. The precipitate was dried in vacuo to give 179.5 mg of a crude peptide product of the desired sequence (H-YERAKSNM-OH). The resulting crude peptide product was subjected to confirmation by HPLC and mass spectrometry with an ESI-TOF/MS instrument.

ESI-MS: Calcd. for M: [M+H]⁺=998.47.

Found M: (m/z): [M+H]⁺=998.4739.

HPLC condition (Condition A)

Column: YMC-triart C18 3 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.7 mL/min, Temperature: 30° C. Detection wavelength: 205 nm for target peptide (8) and analogue peptide (22) in [Table 14-2], or 274 nm Gradient: 2% B (0 min)→2% B (0.2 min)→6.4% B (0.5 min)→6.4% B (11 min)→95% B (15.5 min)→95% B (20.5 min)→2% B (20.6 min)→2% B (29 min) Retention time: around 13.3 min Method for producing (12) Ac-ALRAL-NH₂ (Method B) (1) To a column made of PP, attached to the peptide synthesizer “KMS-3” was added 348.8 mg (0.15 mmol) of Fmoc-NH-SAL resin (WATANABE CHEMICAL INDUSTRIES, LTD., approx. 0.43 mmol/g). Five milliliters of DMF was added thereto, and the mixture was shaken and stirred for 1 minute, and allowed to stand overnight. After removal of the DMF by suction filtration, to the residue was added 3 mL of a solution of 20% piperidine in DMF, and the mixture was shaken and stirred for 35 minutes. The liquid was filtered off by suction, and the residue was washed 5 times with 3 mL of DMF. (2) To the residue were added 2 mL of a solution of Fmoc-Leu-OH in DMF (187.5 mM)(0.375 mmol; 2.5 equivalents), 1 mL of a solution of 1-hydroxybenzotriazole in DMF (375 mM) (0.375 mmol; 2.5 equivalents), and 58 μL of DIC (0.375 mmol; 2.5 equivalents), and then the mixture was shaken and stirred for 3 hours. After removal of the liquid by suction filtration, the residue was washed 5 times with 3 mL of DMF. To the residue was added 3 mL of a solution of 20% piperidine in DMF, and the mixture was shaken and stirred for 35 minutes. The liquid was filtered off by suction, and the residue was washed 5 times with 3 mL of DMF. (3) With Reference to the step (2) above, the subsequent amino acids were sequentially coupled. The order and reaction time of the subsequent amino acids were Fmoc-Ala-OH 2.5 h, Fmoc-Arg(Pbf)-OH 15.5 h, Fmoc-Leu-OH 2.5 h, and Fmoc-Ala-OH 2.5 h. After synthesis of the protected peptide resin whose N-terminus is free amino group, 3 mL of a solution of N-hydroxysuccinic acid in DMF (0.744 mmol; 4.96 equivalents) (248 mM), 43 μL of acetic acid (0.75 mmol; 5 equivalents) and 116 μL of DIC (0.75 mmol; 5 equivalents) were added, and the mixture was shaken and stirred for 16 hours. The liquid was filtered off by suction, and the residue was washed 5 times with 3 mL of DMF and then washed 3 times with 3 mL of MTBE. (4) To the resulting protected peptide resin was added 3 mL of a solution for deprotection (TFA/water/TIS=95/2.5/2.5) under ice cooling, and the ice bath was removed and the mixture was shaken and stirred at ambient temperature for 4 hours. The resin was filtered off and washed three times with the solution for deprotection. The filtrate combined with the washings was concentrated by an evaporator. To the residue was added 5 mL of MTBE, and the mixture was stirred overnight under ice cooling. The entire amount of the mixture was transferred to a centrifuge tube, and centrifuged at 3000 rpm for 1 minute, and then the supernatant was removed. To the precipitate was added 2 mL of MTBE, and the mixture was shaken and stirred for 3 minutes, centrifuged at 3000 rpm for 1 minute, and then the supernatant was removed, which was repeated 3 times. The precipitate was dried in vacuo to give 90.6 mg of a crude peptide product of the desired sequence (Ac-ALRAL-NH₂). The resulting crude peptide product was subjected to confirmation by HPLC and mass spectrometry with an ESI-TOF/MS instrument.

ESI-MS: Calcd. for M: [M+H]⁺=584.39.

Found M: (m/z): [M+H]⁺=584.3879.

HPLC Condition (Condition B) Column: YMC-PackProCl8 3 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 5% B (0 min)→5% B (5 min)→95% B (17 min)→5% B (17.1 min)→5% B (20.1 min)→5% B (24 min) Retention time: around 10.6 min

Method for Producing (1) Ac-YFYPEL-NH₂

According to the procedures of Method B, Fmoc-Leu-OH, Fmoc-Glu(tBu)-OH, Fmoc-Pro-OH, Fmoc-Tyr(tBu)-OH, Fmoc-Phe-OH, and Fmoc-Tyr(tBu)-OH were sequentially coupled to 233 mg of Fmoc-NH-SAL resin (0.1 mmol), followed by the Ac protection of the free amino group at the N-terminus to provide a protected peptide resin. Excision from the resin was performed using a solution for deprotection (TFA/Water/TIS=95/2.5/2.5), followed by a similar way to Method B to provide 90.6 mg of a crude peptide product of the desired sequence (Ac-YFYPEL-NH₂). The resulting crude peptide product was subjected to confirmation by HPLC and mass spectrometry with an ESI-TOF/MS instrument.

ESI-MS: Calcd. for M: [M+H]⁺=872.42.

Found M: (m/z): [M+H]⁺=872.4203.

HPLC condition (Condition C)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 20% B (0 min)→20% B (12 min)→95% B (15 min)→95% B (19 min)→20% B (20 min)→20% B (28 min) Retention time: around 10.2 min

Using the methods A or B described above, the target peptides in the tables below were synthesized by solid phase method, respectively. The HPLC analyses were performed with the following conditions in addition to the above HPLC conditions (Conditions A-C).

HPLC condition (Condition D)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 275 nm Gradient: 15% B (0 min)→25% B (1 min)→25% B (12 min)→95% B (14.5 min)→95% B (17 min)→15% B (17.5 min)→15% B (28 min) HPLC condition (Condition E)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.7 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 20% B (0 min)→35% B (17 min)→95% B (18 min)→95% B (20 min)→20% B (20.5 min)→20% B (28 min) HPLC condition (Condition F)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 279 nm Gradient: 36% B (0 min)→36% B (12.5 min)→95% B (13 min)→95% B (14.5 min)→36% B (15 min)→36% B (27 min) HPLC condition (Condition G)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 281 nm Gradient: 22% B (0 min)→25% B (2 min)→25% B (14 min)→95% B (17 min)→95% B (18.5 min)→22% B (19 min)→22% B (30 min) HPLC condition (Condition H)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.65 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 2% B (0 min)→2% B (3 min)→5% B (12 min)→5% B (14 min)→8% B (16 min)→95% B (19 min)→95% B (19.9 min)→2% B (20 min)→2% B (28 min) HPLC condition (Condition I)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 23% B (0 min)→25% B (2 min)→25% B (10 min)→35% B (15 min)→95% B (17 min)→95% B (19 min)→23% B (20 min)→23% B (28 min) HPLC condition (Condition J)

Column: Waters Atlantis T3 3 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 1.0 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 20% B (0 min)→20% B (12 min)→95% B (17 min)→95% B (19 min)→20% B (19.1 min)→20% B (28 min) HPLC condition (Condition K)

Column: Waters Xbridge Phenyl 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 1.0 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 5% B (0 min)→5% B (3 min)→95% B (20 min)→5% B (20.1 min)→5% B (26 min) HPLC condition (Condition L)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 28% B (0 min)→38% B (12 min)→95% B (15 min)→95% B (19 min)→28% B (20 min)→28% B (28 min) HPLC condition (Condition M)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.65 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 4% B (0 min)→4% B (3 min)→7% B (8 min)→95% B (15 min)→95% B (15.9 min)→4% B (16 min)→4% B (28 min) HPLC condition (Condition N)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 1.0 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 0% B (0 min)→3% B (8 min)→95% B (25 min)→95% B (28 min)→0% B (28.5 min)→0% B (35 min) HPLC condition (Condition 0)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 25% B (0 min)→25% B (14 min)→95% B (17 min)→95% B (21 min)→0% B (22 min)→0% B (32 min) HPLC condition (Condition P)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 20% B (0 min)→25% B (12 min)→25% B (14 min)→95% B (17 min)→95% B (18.5 min)→20% B (19 min)→20% B (28 min) HPLC condition (Condition Q)

Column: Waters Xbridge C18 3.5 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 3% B (0 min)→5% B (5 min)→5% B (16 min)→95% B (17 min)→95% B (19 min)→3% B (19.1 min)→3% B (28 min) HPLC condition (Condition R)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.6 mL/min, Temperature: 30° C. Detection wavelength: 275 nm Gradient: 11% B (0 min)→11% B (10 min)→20% B (12 min)→95% B (15 min)→95% B (17.5 min)→11% B (18 min)→11% B (28 min) HPLC condition (Condition S)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.6 mL/min, Temperature: 30° C. Detection wavelength: 281 nm Gradient: 29% B (0 min)→29% B (10 min)→40% B (12 min)→95% B (15 min)→95% B (17.5 min)→29% B (18 min)→29% B (28 min) HPLC condition (Condition T)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.7 mL/min, Temperature: 30° C. Detection wavelength: 276 nm Gradient: 10.5% B (0 min)→10.5% B (10 min)→95% B (14 min)→95% B (17 min)→10.5% B (17.1 min)→10.5% B (28 min) HPLC condition (Condition U)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.65 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 15% B (0 min)→15% B (10 min)→30% B (12 min)→95% B (15 min)→95% B (17.5 min)→15% B (17.6 min)→15% B (29 min) HPLC condition (Condition V)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 1 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 17% B (0 min)→17% B (12 min)→95% B (17 min)→95% B (19 min)→17% B (19.1 min)→17% B (26 min) HPLC condition (Condition W)

Column: YMC Triart C18 3 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 5% B (0 min)→95% B (17 min)→5% B (17.1 min)→5% B (23.5 min) HPLC condition (Condition X)

Column: YMC-PackproC18RS 3 μm, 50×3 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.5 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 5% B (0 min)→95% B (12 min)→95% B (18 min)→5% B (18.5 min)→5% B (25 min) HPLC condition (Condition Y)

Column: YMC Triart C18 3 μm, 50×3.0 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.65 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 2% B (0 min)→2% B (6 min)→5% B (8 min)→8% B (16 min)→95% B (19 min)→95% B (22 min)→2% B (22.1 min)→2% B (28 min) HPLC condition (Condition Z)

Column: Waters Xbridge C18 3.5 μm, 150×4.6 mm

Mobile phase: A=0.1% aqueous solution of TFA; B=0.1% TFA in acetonitrile Flow rate: 0.7 mL/min, Temperature: 30° C. Detection wavelength: 205 nm Gradient: 10% B (0 min)→10% B (0.2 min)→34% B (0.5 min)→34% B (14 min)→95% B (16 min)→95% B (19 min)→10% B (19.1 min)→10% B (29 min)

TABLE 2-1 Resin  Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Target peptide of resin method Yield Found M for M condition RT  (1) Ac—YFYPEL—NH₂ Resin B Method B  78 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 872.4203 872.42 C 10.2 min  (2) H—YFYPEL—NH₂ Resin B Method B  83 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 830.4064 830.41 D 11.8 min  (3) H—VIRALRRALVALR Resin A Method A 366 mg [M + 2H]²⁺ [M + 2H]²⁺  Condition around ALR—OH 187.5 mg 924.1176 924.11 E 14.5 min  (4) H—ARLDVASEFRKKW Resin B Method B 267 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around NKALSR—NH₂ 233 mg 820.8034 820.80 C 9.2 min  (5) H—HAEGTFTSDVSSY Resin A Method A 440 mg [M + 3H]³⁺ [M + 3H]³⁺  Condition around LEGQAAKEFIAWLVKGRG— 125 mg 1118.8891 1118.90 F 10.4 min OH  (6) H—AGCKNFFWKTFTS Resin A Method A 206 mg [M + 2H]²⁺ [M + 2H]²⁺  Condition around C—OH 125 mg 820.3680 820.37 G 16.6 min [M + 2H]²⁺ [M + 2H]²⁺  Condition around 820.3734 820.37 S 8.4 min  (7) H—AQKLRASD—OH Resin A Method A 183 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 888.4879 888.49 H 17.2 min Condition around M 9.2 min  (8) H—YERAKSNM—OH Resin A Method A 179 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 888.4879 888.49 A 13.4 min  (9) H—FRVDEEFQSPFAS Resin B Method B 313 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around QSRGYFLFRPRN—NH₂ 233 mg 1027.1906 1027.18 I 9.8 min (12) Ac—ALRAL—NH₂ Resin B Method B 105 mg [M + H]⁺ [M + H]⁺ Condition around 348.8 mg 584.3876 584.39 B 10.4 min (13) Ac—ALRAL—OH Resin A Method A 124 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 585.3720 585.37 B 10.6 min

TABLE 2-2 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Target peptide of resin method Yield Found M for M condition RT (14) H—ALRALRALR—OH Resin A Method A 213 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 1039.6851 1039.68 J 9.7 min (15) Ac—GGRGG—NH₂ Resin B Method B 115 mg [M + H]⁺ [M + H]⁺ Condition around 348.8 mg 444.2319 444.23 K 2.2 min (16) H—HSDGTFTSELSRL Resin B Method B 313 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around REGARLQRLLQGLV—NH₂ 233 mg 1013.5576 1013.56 L 7.2 min (11) H—GGGRG—NH₂ Resin B Method B  72 mg [M + H]⁺ [M + H]⁺ Condition around 348.8 mg 402.2181 402.22 N 3.2 min (17) Pyr—HWSYILRP— Resin B Method B 134 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around NH₂ 233 mg 591.3131 591.31 O 13.4 min Condition around P 7.9 min (18) H—HVTTV—NH₂ Resin B Method B  67 mg [M + H]⁺ [M + H]⁺ Condition around 189 mg 555.3249 555.32 Q 8.7 min (19) H—YERAKSNM—NH₂ Resin B Method B 134 mg [M + H]⁺ [M + H]⁺ Condition around 222 mg 997.4871 997.49 R 4.8 min

TABLE 2-3 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Target peptide of resin method Yield Found M for M condition RT (20) H—VKRESYSGVT— Resin B Method  101 mg [M + H]⁺ [M + H]⁺ Condition around NH₂ 189 mg B 1124.6058 1124.61 T 10.1 min (21) H—RAVLP—OH Resin A Method 52.5 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg A 555.3611 555.36 U 14.4 min (22) H—(RC8)RRR((Me) Resin B Method   99 mg [M + H]⁺ [M + H]⁺ Condition around F)R(SC5)—NH₂ 222 mg B 1123.7689 1123.77 W 7.6 min (27) Ac—YHYPEL—NH₂ Resin B Method   79 mg [M + H]⁺ [M + H]⁺ Condition around 222 mg B 862.4088 862.41 V 12.8 min (28) Ac—Y(MeK)YPEL— Resin B Method   93 mg [M + H]⁺ [M + H]⁺ Condition around NH₂ 222 mg B 867.4607 867.46 V 11.7 min (23) Ac—HYFYPEL—NH₂ Resin B Method  106 mg [M + H]⁺ [M + H]⁺ Condition around 222 mg B 1009.4756 1009.48 X 7.5 min (24) H—WPVTLNAQTID— Resin B Method  114 mg [M + H]⁺ [M + H]⁺ Condition around NH₂ 222 mg B 1256.6613 1256.66 X 7.3 min (25) H—T((Me)G)RK Resin A Method  163 mg [M + H]⁺ [M + H]⁺ Condition around (Dap)H—OH 125 mg A 698.4059 698.41 Y 9.7 min (26) Pyr—GPWLEEEEEAY Resin B Method  215 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around GWMDF—NH₂ 233 mg B 1049.4321 1049.43 Z 16.0 min

Similarly, the analogue peptides shown in the tables below were synthesized by solid phase method using the above methods.

TABLE 3-1 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Analogue peptide of resin method Yield Found M for M condition RT  (1) Ac—YYPEL—NH₂ Resin B Method B  65 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 725.3501 725.35 C 1.9 min Condition around V 16.0 min  (2) H—YYPEL—NH₂ Resin B Method B  80 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 683.3391 683.34 D 8.5 min  (3) H—VIRALRALVALRA Resin A Method A 354 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around LR—OH 187.5 mg 846.0698 846.07 E 13.6 min  (4) H—ARLDVASEFRKKN Resin B Method B 258 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around KALSR—NH₂ 233 mg 758.7746 758.77 C 2.3 min  (5) H—HAEGTFTSDVSSY Resin A Method A 464 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around LEGQAAKEFAWLVKGRG—OH 125 mg 1081.2033 1081.20 F 5.7 min  (6) H—AGCKNFFWKTF Resin A Method B 382 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around TS—OH 125 mg 768.8683 768.87 G 14.2 min  (7) H—AQKLRAD—OH Resin A Method A 127 mg [M + H]⁺ [M + H]⁺ Condition 17.0 min 187.5 mg 801.4588 801.46 H  (8) H—AKLRAD—OH Resin A Method A 115 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 673.4015 673.40 H 15.7 min (19) H—QKLRASD—OH Resin A Method A  45 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 817.4480 817.45 M 11.5 min (20) H—AQKLRSD—OH Resin A Method A 151 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 817.4547 817.45 M 5.2 min (21) H—AQKLRAS—OH Resin A Method A 201 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 773.4053 773.46 M 7.3 min

TABLE 3-2 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Analogue peptide of resin method Yield Found M for M condition RT (24) H—AQKRASD—OH Resin A Method A  42 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 775.4053 775.41 M 5.2 min  (9) H—YERAKNM—OH Resin A Method A 152 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 911.4377 911.44 A 7.3 min (13) H—YERKSNM—OH Resin A Method A 124 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 927.4348 927.44 A 11.4 min (14) H—YERASNM—OH Resin A Method A 147 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 870.3745 870.38 A 12.4 min (16) H—YERAKSM—OH Resin A Method A 150 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 884.4260 884.43 A 6.9 min (22) H—ERAKSNM—OH Resin A Method A  90 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 835.4087 835.41 A 4.3 min (23) H—YERAKSN—OH Resin A Method A 175 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 867.4312 867.43 A 14.0 min (10) H—FRVDEEFQSPFAS Resin B Method B 289 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around QSRGYFLFRRN—NH₂ 233 mg 994.8306 994.83 I 8.8 min (12) Ac—ALAL—NH₂ Resin B Method B  67 mg [M + H]⁺ [M + H]⁺ Condition around 348.8 mg 428.2874 428.29 B 10.6 min (15) Ac—ALAL—OH Resin A Method A  30 mg [M + H]⁺ [M + H]⁺ Condition around 1258 mg 429.2710 429.27 B 11.0 min (17) H—ALALRALR—OH Resin A Method A 224 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg 883.5824 883.58 J 12.0 min (18) Ac—GGGG—NH₂ Resin B Method B  30 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 288.1300 288.13 K 2.3 min (30) H—HSDGTFTSELSRL Resin B Method B 289 mg [M + 3H]³⁺ [M + 3H]³⁺ Condition around EGARLQRLLQGLV—NH₂ 233 mg 961.5224 961.52 L 9.7 min (11) H—GGGG—NH₂ Resin B Method B  69 mg [M + H]⁺ [M + H]⁺ Condition around 348.8 mg 246.1180 246.12 N 1.9 min (26) Pyr—HWSYLLRP— Resin B Method B 143 mg [M + 2H]²⁺  [M + 2H]²⁺  Condition around NH₂ 233 mg 591.3136 591.31 O 10.0 min

TABLE 3-3 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Analogue peptide of resin method Yield Found M for M condition RT (31) Pyr—HWSYILLRP— Resin B Method B 129 mg [M + H]⁺ [M + H]⁺ Condition around NH₂ 233 mg 1294.7055 1294.72 P 14.2 min (32) H—VTTV—NH₂ Resin B Method B  49 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 418.2660 418.28 Q 5.2 min (33) H—hVTTV—NH₂ Resin B Method B  61 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg 555.3249 555.32 Q 10.9 min (34) H—YERAKSNL—NH₂ Resin B Method B 119 mg [M + H]⁺ [M + H]⁺ Condition around 222 mg 979.5310 979.53 R 6.8 min (35) H—AGcKNFFWKTPT Resin A Method A 129 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around SC—OH 125 mg 820.3865 820.37 S 7.4 min

TABLE 3-4 Resin Confirmation test used ESI-MS HPLC Amount Synthesis Calcd. Analysis Analogue peptide of resin method Yield Found M for M condition RT (36) H—VKRESYSGV—NH₂ Resin B Method 105 mg [M + H]⁺ [M + H]⁺ Condition around 233 mg B 1023.5577 1023.56 T 8.8 min (37) H—RALP—OH Resin A Method  45 mg [M + H]⁺ [M + H]⁺ Condition around 187.5 mg A 456.2926 456.29 U 5.8 min (38) H—(RC8)RRRR Resin B Method 119 mg [M + H]⁺ [M + H]⁺ Condition around (SC5)—NH₂ 222 mg B 962.6858 962.68 W 6.6 min (39) Ac—HYYPEL—NH₂ Resin B Method  93 mg [M + H]⁺ [M + H]⁺ Condition around 222 mg B 862.4114 862.41 X 6.9 min (40) H—PVTLNAQTID— Resin B Method 119 mg [M + H]⁺ [M + H]⁺ Condition around NH₂ 233 mg B 1070.5823 1070.58 X 6.6 min (41) H—((Me)G)RK Resin A Method 134 mg [M + H]⁺ [M + H]⁺ Condition around (Dap)H—OH 125 mg A 597.3584 597.36 Y 6.8 min (42) Pyr—GPWLEEEEEY Resin B Method 222 mg [M + 2H]²⁺ [M + 2H]²⁺ Condition around GWMDF—NH₂ 233 mg B 1013.9123 1013.91 Z 14.2 min

1-2: Acid Compound

The following acid compounds were purchased to use.

Sulfuric acid: NACALAI TESQUE, INC., special grade; Hydrochloric acid: NACALAI TESQUE, INC., 0.1 N special grade;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

NACALAI TESQUE, INC., special grade;

Wako Pure Chemical, special grade;

Tokyo Chemical Industry Co., Ltd.;

NACALAI TESQUE, INC., first grade;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.;

Tokyo Chemical Industry Co., Ltd.

Unless otherwise stated, the following sulfonic acids were synthesized by reacting the corresponding halides with sodium sulfite and subjecting the resulting sulfonic acid sodium salts to acidification with hydrochloric acid.

As a specific example, the synthesis of p-methylbenzyl sulfonic acid is described below:

p-Methylbenzyl bromide 1.55 g (7 mmol) was dissolved in 4 mL of ethanol. To the mixture was added 0.97 g of sodium sulfite (7.7 mmol; 1.1 equivalents) and 8 mL of water. The mixture was heated at reflux overnight. After the reaction, the mixture was concentrated by an evaporator to remove ethanol, and the precipitated solid was filtered to give 1.09 g of p-methylbenzylsulfonic acid sodium salt. To 625 mg of the resulting solid were added 1 mL of concentrated hydrochloric acid and 1.5 mL of water, and the mixture was stirred overnight. The liquid was filtered off. The residue was washed 2 times with 0.5 mL of water to give 448 mg of p-methylbenzyl sulfonic acid. ¹H NMR (400 MHz, D₂O) 7.25 (d, J=8.0 Hz, 2H), 7.19 (d, J=7.9 Hz, 2H), 4.07 (s, 2H), 2.28 (s, 3H).

was prepared from the corresponding alcohol compound as follows. 1. In a 50 mL 3-necked flask, 1.18 g (6 mmol) of 9-fluorenyl methanol was dissolved in 9 mL of ethyl acetate, and cooled to 0° C. in an ice bath. To the mixture was added 488 μL (6.3 mmol; 1.05 eq) of methanesulfonyl chloride. 920 μL (6.6 mmol; 1.05 eq) of triethylamine was added dropwise thereto at an internal temperature of 0 to 10° C. After stirring at 0° C. for 26 hours, 10 mL of water and 10 mL of MTBE were added to quench the reaction. The separated organic layer was washed sequentially with 15 mL of saturated aqueous sodium hydrogen carbonate, 15 mL of 0.5 M aqueous sodium hydrogen sulfate, and 15 mL of water. Then the resulting organic layer was concentrated to give 1.28 g of a crude 9-fluorenylmethoxymethanesulfonate. ¹H NMR (400 MHz, CDCl₃) δ: 7.78 (d, J=7.8 Hz, 2H), 7.62 (d, J=7.8 Hz, 2H), 7.43 (m, 4H), 4.50 (d, J=7.6 Hz, 2H), 4.31 (t, J=7.6 Hz, 1H), 2.91 (s, 3H). 2. To 1.28 g of the resulting crude 9-fluorenylmethoxymethanesulfonate was added 3 mL of ethanol, and then to the resulting solution were added 7 mL of water and 1.01 g (8 mmol) of sodium sulfite. The mixture was heated and stirred at an internal temperature of 80° C. for 90 h. After the reaction was completed, the reaction mixture was concentrated by an evaporator to remove ethanol, and the precipitated solid was filtered off. To the filtrate was added 1 mL of concentrated hydrochloric acid, and the mixture was evaporated to dryness. To the residue was added 2 mL of water, and the mixture was suspended for 1 hour, and filtered, and the resulting residue was washed with 0.5 mL of water 2 times to give 310 mg of 9-fluorenylmethylsulfonic acid (′H NMR (400 MHz) (CD₃OD) 7.91 (d, J=7.6 Hz, 2H), 7.78 (d, J=7.6 Hz, 2H), 7.34 (m, 4H), 4.44 (t, J=6.0 Hz, 1H), 3.28 (m, 2H)).

According to the above synthesis of

805 mg of 2-indanol (6 mmol) was used as a starting material to give 1.26 g of 2-indanyloxymethanesulfonate (¹H NMR (400 MHz, CDCl₃) δ: 7.22 (m, 4H), 5.53 (m, 1H), 3.37 (m, 1H), 3.21 (m, 2H), 3.02 (s, 3H)), and 1.26 g of the resulting 2-indanyloxymethanesulfonate was used to give 131 mg of 2-indanylsulfonic acid:

(¹H NMR (400 MHz) (CD₃OD) 7.19 (m, 2H), 7.12 (m, 2H), 3.80 (m, 1H), 3.34 (m, 3H)).

According to the above procedure for the synthesis of p-methylbenzylsulfonic acid, the sulfonic acids shown in the tables below were synthesized using the corresponding halides.

TABLE 4-1 Sulfonic acid Halide Yield ¹H NMR (400 MHz)

0.15 g (D₂O) 7.71 (m, 4H), 7.66 (t, J = 7.6 Hz, 1H), 7.50 (m, 4H), 4.22 (s, 2H)

0.95 g (CD₃OD) 7.23 (m, 4H), 7.15 (t, J = 7.0 Hz, 1H), 2.75 (m, 4H), 2.09 (m, 2H)

0.21 g (CD₃OD) 8.02 (d, J = 8.2 Hz, 2H), 7.33 (d, J = 7.9 Hz, 2H), 4.48 (s, 2H), 2.43 (s, 3H)

0.26 g (CD₃OD) 7.20 (t, J = 7.9 Hz, 1H), 7.00 (m, 2H), 6.81 (m, 1H), 4.02 (s, 2H), 3.79 (s, 3H)

0.47 g (CD₃OD) 8.18 (d, J = 9.2 Hz, 2H), 7.65 (d, J = 9.2 Hz, 2H), 4.17 (s, 2H)

TABLE 4-2

0.32 g (CD₃OD) 7.96 (d, J = 8.2 Hz, 2H), 7.54 (d, J = 8.3 Hz, 2H), 4.12 (s, 2H), 3.89 (s, 3H)

0.46 g (CD₃OD) 7.87 (m, 4H), 7.61 (m, 1H), 7.46 (m, 2H), 4.24 (s, 2H)

0.16 g (D₂O) 8.17 (d, J = 7.6 Hz, 1H), 7.92 (t, J = 8.0 Hz, 2H), 7.55 (m, 4H), 4.66 (s, 2H)

0.24 g (D₂O) 7.26 (m, 4H), 7.18 (m, 1H), 3.05 (m, 4H)

0.13 g (D₂O) 7.33 (s, 4H), 4.09 (s, 4H)

0.53 g (CD₃OD) 2.81 (t, J = 7.8 Hz, 2H), 2.21 (m, 3H), 1.90 (m, 2H), 1.64 (m, 2H)

TABLE 4-3

0.15 g (DMSO-d₆) 9.40 (s, 1H), 7.17 (m, 2H), 7.05 (t, J = 7.4 Hz, 1H), 6.92 (t, J = 7.6 Hz, 1H), 3.32 (dd, J = 8.6 Hz, 11.0 Hz, 1H), 2.67 (m, 2H), 2.39 (m, 2H)

1.50 g (CD₃OD) 7.27 (m, 8H), 7.16 (m, 2H), 4.07 (t, J = 8.0 Hz, 1H), 2.72 (m, 2H), 2.53 (m, 2H)

0.19 g (DMSO-d₆) 3.13 (s, 6H), 2.43 (s, 9H)

67 mg (CD₃OD) 7.12 (d, J = 6.4 Hz, 2H), 6.82 (d, J = 6.8 Hz, 2H), 3.75 (s, 3H), 2.77 (m, 2H), 2.66 (t, J = 7.5 Hz, 2H), 2.05 (m, 2H)

0.18 g (CD₃OD) 7.07 (d, J = 7.7 Hz, 1H), 6.99 (t, J = 7.8 Hz, 1H), 6.72 (m, 2H), 2.80 (m, 2H), 2.71 (t, J = 7.4 Hz, 2H), 2.08 (m, 2H)

TABLE 4-4

0.84 g (CD₃OD) 7.23 (m, 4H), 7.15 (t, J = 7.1 Hz, 1H), 6.72 (m, 2H), 2.83 (dd, J = 8.0 Hz, 7.4 Hz, 1H), 2.65 (t, J = 7.4 Hz, 2H), 1.86-1.73 (m, 4H)

1.05 g (CD₃OD) 7.33 (m, 4H), 4.01 (s, 2H), 1.30 (s, 9H)

67 mg (CD₃OD) 6.75 (m, 2H), 6.67 (m, 1H), 3.70 (s, 3H), 3.67 (s, 3H), 2.55 (m, 4H), 1.88 (m, 2H)

 6 mg (DMSO-d₆) 6.98 (s, 2H), 5.06 (s, 1H), 2.85 (m, 2H), 2.68 (t, J = 7.3 Hz, 2H), 2.14 (m, 2H)

TABLE 4-5

7 mg (CD₃OD) 7.42 (m, 8H), 7.34 (m, 2H), 2.91 (m, 2H), 2.81 (m, 2H)

126 mg (DMSO-d₆) 8.74 (dd, J = 8.1 Hz, 1.2 Hz, 1H), 7.48 (m, 4H), 7.30 (t, J = 6.4 Hz, 1H), 7.22 (t, J = 6.0 Hz, 1H), 7.12 (m, 7H)

21 mg (CD₃OD) 8.03 (s, 1H), 7.99 (dd, J = 9.0 Hz, 2.7 Hz, 1H), 6.88 (d, J = 9.0 Hz, 1H), 4.30 (t, J = 5.2 Hz, 2H), 2.89 (t, J = 6.4 Hz, 2H), 2.05 (m, 2H)

345 mg (CD₃OD) 7.43 (d, J = 8.2 Hz, 2H), 7.17 (d, J = 8.2 Hz, 2H), 2.74 (m, 4H), 2.09 (m, 2H)

TABLE 4-6

302 mg (CD₃OD) 8.15 (t, J = 1.8 Hz, 1H), 8.09 (m, 1H), 7.69 (d, J = 7.5 Hz, 1H), 7.55 (t, J = 7.9 Hz, 1H), 2.93 (t, J = 7.8 Hz, 2H), 2.85 (t, J = 7.6 Hz, 2H), 2.16 (m, 2H)

338 mg (CD₃OD) 7.55 (s, 1H), 7.50 (m, 3H), 2.85 (m, 4H), 2.13 (m, 2H)

85 mg (CD₃OD) 7.43 (s, 3H), 4.13 (s, 6H)

833 mg (CD₃OD) 7.70 (dd, J = 6.5 Hz, 1.9 Hz, 2H), 7.50 (dd, J = 6.5 Hz, 1.9 Hz, 2H), 4.15 (s, 2H)

TABLE 4-7

80 mg (CD₃OD) 7.25 (m, 4H), 7.16 (t, J = 6.8 Hz, 1H), 2.83 (m, 3H), 2.35 (m, 1H), 1.76 (m, 1H), 1.37 (d, J = 6.8 Hz, 3H)

40 mg (CD₃OD) 5.84 (m, 1H), 5.03 (m, 2H), 2.81 (t, J = 9.8 Hz, 2H), 2.20 (m, 2H), 1.90 (m, 2H)

424 mg (CD₃OD) 7.44 (d, J = 7.2 Hz, 2H), 7.32 (m, 2H), 7.22 (m, 1H), 6.64 (d, J = 15.8 Hz, 1H), 6.40 (dd, J = 15.8 Hz, 7.8 Hz, 1H), 3.70 (d, J = 7.8 Hz, 2H)

TABLE 4-8

361 mg (CD₃OD) 7.32 (m, 4H), 7.24 (m, 6H), 4.74 (m, 1H), 2.93 (m, 4H)

Synthesis of Benzylsulfonic Acid

To 1.71 g (10 mmol) of benzyl bromide were added 10 mL of ethanol and 0.76 g (10 mmol) of thiourea, and heated at reflux overnight. After the disappearance of the starting materials was confirmed by TLC, the mixture was concentrated and dried by an evaporator. To the residue was added 10 mL of acetonitrile to give a solution, and the solution was cooled in an ice bath. To the solution were added 2 mL of 2N hydrochloric acid (4 mmol) and 5.34 g of N-chlorosuccinimide (40 mmol) under ice cooling, and the mixture was stirred at room temperature for 1 hour. The reaction mixture was concentrated by an evaporator, and to the residue was added 5 mL of ethyl acetate, and the separated organic layer was concentrated by an evaporator. To the residue were added 5 mL of MTBE and 5 mL of heptane, the precipitated solid was filtered off, and the filtrate was concentrated by an evaporator. The residue was purified by silica gel column chromatography (Silica gel: Fuji SILYSIA CHEMICAL LTD, PSQ-100B, 50 g; Mobile phase: hexane/ethyl acetate=20/1) to give 0.64 g of benzylsulfonyl chloride. To 0.59 g of the resulting benzylsulfonyl chloride was added 5.9 mL of water, and the mixture was heated at reflux for 5 days. The reaction mixture was concentrated to dryness and dried by a vacuum pump to give 0.39 g of benzylsulfonic acid. ¹H NMR (400 MHz, CD₃OD) 7.42 (m, 2H), 7.28 (m, 3H), 4.05 (s, 2H)

Synthesis of p-Carboxybenzylsulfonic Acid

To 0.50 g of p-methoxycarbonylbenzylsulfonic acid synthesized above, 0.6 mL of concentrated hydrochloric acid and 0.6 mL of water were added and the mixture was heated to 90° C. The mixture was heated with stirring at 90° C. overnight, then cooled to room temperature, and then filtered under reduced pressure to collect the precipitated solid to give 0.37 g of p-carboxybenzylsulfonic acid. ¹H NMR (400 MHz, CD₃OD) 7.97 (d, J=8.3 Hz, 2H), 7.53 (d, J=8.2 Hz, 2H), 4.12 (s, 2H)

Abbreviations

TFA: trifluoroacetic acid IPA: isopropyl alcohol DMSO: dimethyl sulfoxide DIC: diisopropylcarbodiimide TIS: triisopropylsilane MTBE: methyl tert-butyl ether

Test Example 1: Purification of Target Peptide-1 (for Removal of Analogue Peptide)

A crude target peptide and a crude analogue peptide prepared in the above 1-1 were dissolved in 1% TFA in water/acetonitrile=100 to 70/0 to 30, to give 20 mM crude target peptide solution and 20 mM crude analogue peptide solution, respectively (assuming 100% purity of each peptide). Poorly soluble peptides were diluted to about 5 mM (assuming 100% purity of each peptide) and dissolved.

Each acid compound was dissolved in water, or in 10% IPA aqueous solution or 10% DMSO aqueous solution in case where it was difficult to dissolve in water, to give 50 mM acid compound solution.

The crude target peptide solution (1 μmol, assuming 100% purity of the target peptide) and the crude analogue peptide solution (0.1 μmol, assuming 100% purity of the analogue peptide) were mixed. The mixture was mixed with an acid compound solution (1.5 μmol) (the resulting mixture was analyzed by HPLC to provide the value of “before treatment”). The mixture was dried by lyophilization.

To the residue was added 100 μL of IPA, and the mixture was shaken overnight at room temperature.

The resulting slurry was centrifuged (5000 to 15000 rpm, 1 to 5 min), and the resulting cake was washed with 150 μL of IPA 2 times. The filtrate and the washings were combined.

The resulting solid and the filtrate combined with the washings were analyzed by HPLC to provide the values of “solid obtained after treatment” and “filtrate obtained after treatment”.

HPLC instruments were the same as those described above.

Measurement conditions: the same as the HPLC conditions A to Z for peptide synthesis.

For peptides comprising aromatic amino acid residue(s), long-wavelength ultraviolet absorption can be attributed exclusively to the aromatic side chain(s). The HPLC detection wavelengths for analyzing such peptides were Condition A (for detection at 274 nm), Condition D, Conditions F to G, and Conditions R to T. Under condition A (for detection at 274 nm), condition R, and condition T, both of the target and analogue peptides had 1 aromatic amino acid residue each. Under condition F, both of the target and analogue peptides had 5 aromatic amino acid residues each. Under condition G and condition S, both of the target and analogue peptides had 4 aromatic amino acid residues each. Under condition D, the target peptide had 3 aromatic amino acid residues, and the analogue peptide had 2 aromatic amino acid residues. That is, the number of aromatic side chains contributing to the long-wavelength ultraviolet absorption at 274 to 281 nm was the same or 1 difference between the target peptide and the analogue peptide, and the ratio of the HPLC area values can be regarded as an approximate molar ratio.

On the other hand, a peptide not comprising an aromatic amino acid residue has no ultraviolet absorption on a long wavelength side, and a short wavelength ultraviolet absorption (205 nm) attributed to a carbonyl group can be used for detection. For example, the target peptide had 10 carbonyl groups and the analogue peptide had 9 carbonyl groups in condition A (for detection at 205 nm) and condition J. Similarly, the target peptide has 6 carbonyl groups and the analogue peptide has 5 carbonyl groups in condition B and condition K, the target peptide has 8 carbonyl groups and the analogue peptide has 7 carbonyl groups in condition C, the target peptide has 16 carbonyl groups and the analogue peptide has 15 carbonyl groups in condition E, the target peptide has 9 carbonyl groups and the analogue peptide has 6 or 8 carbonyl groups in condition H, the target peptide has 31 carbonyl groups and the analogue peptide has 30 carbonyl groups in condition I, the target peptide has 32 carbonyl groups and the analogue peptide has 31 carbonyl groups in condition L, the target peptide has 9 carbonyl groups and the analogue peptide has 8 carbonyl groups in condition M. The number of carbonyl groups that contribute to the short-wavelength ultraviolet absorption at 205 nm is only 1 to 3 different between the target peptide and the analogue peptide, accordingly the ratio of the HPLC area values of the target peptide and the analogue peptide can be regarded as the approximate molar ratio. Although the target peptides (9) and (10) have aromatic side chain(s), they are sufficiently long and contain a large number of carbonyl groups, so they were detected by ultraviolet absorption (205 nm) of carbonyl group in condition I, but can also be detected at the long wavelength side (Both of the target peptide and analogue peptide have six aromatic amino acid residues). Similarly, the target peptide (16) and the analogue peptide (25), each of which has 2 aromatic side chains, were detected at 205 nm.

In condition N, condition 0, condition P, condition Q, condition U, condition V, condition W, condition X, condition Y, and condition Z, the short-wavelength ultraviolet absorption (205 nm) of carbonyl group was similarly used for detection.

As shown in the following Equation 1), the ratio (%) of the area of the target peptide to the total area of the target peptide and the analogue peptide was calculated using the HPLC measurement values (Area). The above ratio was regarded as the approximate ratio (%) of the amount of substance (mol) of the target peptide to the total amounts of substance (mol) of the target peptide and the analogue peptide (hereinafter, referred to as “target peptide ratio”).

$\begin{matrix} {{{Target}\mspace{14mu}{peptide}\mspace{14mu}{ratio}\;(\%)} = {{\frac{{Area}\mspace{14mu}{of}\mspace{14mu}{target}\mspace{14mu}{peptide}}{\begin{matrix} {{{Area}\mspace{14mu}{of}\mspace{14mu}{target}\mspace{14mu}{peptide}}\; +} \\ {{Area}\mspace{14mu}{of}\mspace{14mu}{analouge}\mspace{14mu}{peptide}} \end{matrix}} \times 100} \approx \frac{{Tagret}\mspace{14mu}{peptide}\mspace{11mu}({mol})}{\begin{matrix} {{{Tagret}\mspace{14mu}{peptide}\mspace{11mu}({mol})} +} \\ {{Analogue}\mspace{14mu}{peptide}\mspace{11mu}({mol})} \end{matrix}}}} & \left. {{Equation}\mspace{14mu} 1} \right) \end{matrix}$

Examination 1: Investigation of Salt Formation

When a peptide is mixed with an acid compound, the N-terminal amino group or a side chain moiety in a basic amino acid (lysine K, arginine R, histidine H etc.) and the acid compound may form a salt.

Based on the change of target peptide ratio (%) in the solid using the following peptides, whether a salt with the peptide and the acid compound is formed was examined.

Target peptide H-YFYPEL-NH₂, which does not comprise a basic amino acid, and its analogue peptide H-YYPEL-NH₂ having one residue deletion; and

The corresponding peptides which are N-terminally protected with an acetyl group (Ac), target peptide Ac-YFYPEL-NH₂, and analogue peptide Ac-YYPEL-NH₂ having one residue deletion.

In addition, the change of target peptide ratio (%) in the solid was examined using the following peptides, which comprise neither a basic amino acid nor functional group capable of forming a salt:

Target peptide Pyr-GPWLEEEEEAYGWMDF-NH₂ and its analogue peptide Pyr-GPWLEEEEEYGWMDF-NH₂ having one residue deletion.

The change in the ratio of the target peptide (%) was calculated as “Increased point of target peptide ratio (%)” using Equation 2 below.

Increased point of target peptide ratio (%)=target peptide ratio (%) in the solid obtained after treatment−target peptide ratio (%) of before treatment.  Equation 2):

The results are shown in the tables below.

TABLE 5-1 Target peptide Analogue peptide No acid compound Sulfuric acid

(1) Ac-YF (1) Ac-YYP Before Area of target peptide 3778581 3778581 3778581 YPEL—NH₂ EL—NH₂ treatment Area of analogue peptide  280840  280840  280840 Target peptide ratio (%) 93.1% 93.1% 93.1% Solid Area of target peptide 1214330  938194 1191857 obtained Area of analogue peptide  70516  48524  59848 after Target peptide ratio (%) 94.5% 95.1% 95.2% treatment Increased point of  1.4 2.0 2.1 target peptide ratio (%) (2) H-YFY (2) H-YYPE Before Area of target peptide  638016  441924  464222 PEL—NH₂ L—NH₂ treatment Area of analogue peptide  64491  45406  47540 Target peptide ratio (%) 90.8% 90.7% 90.7% Solid Area of target peptide  41395  102094  58715 obtained Area of analogue peptide   4325  10239   3880 after Target peptide ratio (%) 90.5% 90.9% 93.8% treatment Increased point of −0.3 0.2 3.1 target peptide ratio (%)

TABLE 5-2 Target peptide Analogue peptide No acid compound Hydro- chloric acid

(26) Pyr- (42) Pyr- Before Target 89.1% 87.5% 88.9% GPWLEEEEEA GPWLEEEEEYG treatment peptide YGWMDF—NH₂ WMDF—NH₂ ratio (%) Solid Target 89.0% 87.5% 88.9% obtained peptide after ratio treatment (%) Increased point −0.1 0 0 of target peptide ratio (%) Pyr- =

Regarding Table 5-1

Regarding the target peptide Ac-YFYPEL-NH₂ and its analogue peptide Ac-YYPEL-NH₂, wherein the N-terminuses are protected with Ac group, the increased points of target peptide ratio (%) are 1.4 points in the case of no acid compound, 2.0 points in the case of sulfuric acid, 2.1 points in the case of the sulfonic acid compound, indicating that there was no large difference in the increased points of target peptide rate (%) in the presence or absence of an acid compound.

On the other hand, regarding the target peptide: H-YFYPEL-NH₂ and its analogue peptide: H-YYPEL-NH₂, wherein the N-terminuses are free, the increased points of target peptide ratio (%) are −0.3 points in the case of no acid compound, 0.2 points in the case of sulfuric acid, and 3.1 points in the case of the sulfonic acid compound, indicating that the increased point for the sulfonic acid compound was greater than the increased points for no acid compound and sulfuric acid.

When structures of a target peptide and its analogue peptide are similar, the solubility properties of the target peptide and the analogue peptide in a solvent are usually similar. When a peptide forms a solid by forming a salt with a sulfonic acid compound, the solubility property of the solid in the solvent greatly changes as compared with that of the original peptide. Accordingly, in a case where the target peptide exists more than its analogue peptide, the possibility that the target peptide ratio in the solid separated by solid-liquid separation is increased is remarkably increased.

Thus, these results suggest that the sulfonic acid compound formed a salt with the N-terminal amino group of the peptides.

Regarding the case of the target peptide Ac-YFYPEL-NH₂ and its analogue peptide Ac-YYPEL-NH₂, wherein the N-terminuses are protected with Ac group, it is considered that the increase in target peptide ratio (%), regardless of the presence or absence of the acid compound, was caused by the difference in the dissolution behavior of these peptides in IPA.

Regarding Table 5-2

Regarding the case of the target peptide Pyr-GPWLEEEEEAYGWMDF-NH₂ and its analogue peptide Pyr-GPWLEEEEEYGWMDF-NH₂, both of which have no moiety capable of forming a salt, there is no difference of the increased points of target peptide ratio (%) between use of the acid compound and no use of the acid compound.

Examination 2: Effect of Sulfonic Acid Compound

The increased points of the target peptide ratio (%) in the obtained solid were calculated in the same way as described above, using the acid compounds, the target peptides, and the analogue peptides shown in the table below.

The results are shown in the table below.

TABLE 6 Target peptide Analogue peptide No acid compound

(3) H—VIRALRR (3) H—VIRALRAL Before Target peptide 88.8% 89.0% 88.6% ALVALRALR—OH VALRALR—OH treatment ratio (%) Solid obtained Target peptide 88.6% 89.3% 89.0% after treatment ratio (%) Increased point of −0.2  0.3 0.4 target peptide ratio (%) (4) H—ARLDVAS (4) H—ARLDVASSE Before Target peptide 88.5% 88.5% 88.5% EFRKKWNKALSR— FRKKNKALSR— treatment ratio (%) NH₂ NH₂ Solid obtained Target peptide 90.1% 91.9% 92.5% after treatment ratio (%) Increased point of 1.6 3.4 4.0 target peptide ratio (%) (5) H—HAEGTFT (5) H—HAEGTFTS Before Target peptide 80.8% 81.2% 81.5% SDVSSYLEGQAA DVSSYLEGQAAKE treatment ratio (%) KEFIAWLVGRG— FAWLVKGRG—OH Solid obtained Target peptide 80.7% 82.4% 81.7% OH after treatment ratio (%) Increased point of −0.1  1.2 0.2 target peptide ratio (%) (6) H—AGCKNFF (6) H—AGCKNFFW Before Target peptide 89.9% 90.4% 90.6% WKTFTSC—OH KTFTS—OH treatment ratio (%) Solid obtained Target peptide 90.0% 92.5% 93.4% after treatment ratio (%) Increased point of 0.1 2.1 2.8 target peptide ratio (%)

In comparison with the case where no acid compound was used, use of the sulfonic acid compounds increased the increased points of the target peptide ratio (%). These results showed that the sulfonic acid compounds have excellent effects in separating the target peptide and the analogue peptide.

It is considered that this is because the dissolution behavior was changed by the salt formation with the sulfonic acid compounds, as suggested in the Examination 1.

Examination 3: Comparison with Inorganic Acids

The increased points of the ratio (%) of the target peptide in the obtained solid was calculated in the same way as described above, using the acid compounds, the target peptides, and the analogue peptides shown in the table below.

The results are shown in the table below.

TABLE 7 Target peptide Analogue peptide Hydrochloric acid Sulfuric acid

(7) H—AQK (7) H—AQKL Before Target peptide 86.3% 86.4% 89.6% 87.1% LRASD—OH RAD—OH treatment ratio (%) Solid obtained Target peptide 85.4% 84.8% 89.9% 87.5% after ratio (%) treatment Increased point of −0.9 −1.6 0.3 0.4 target peptide ratio (%) (8) H—AKLR Before Target peptide 91.2% 91.2% 94.5% 90.9% AD—OH treatment ratio (%) Solid obtained Target peptide 91.2% 91.7% 97.1% 94.4% after ratio (%) treatment Increased point of  0.0  0.5 2.6 3.5 target peptide ratio (%) (8) H—YER (9) H—YERA Before Target peptide 91.5% 91.2% 90.9% 91.0% AKSNM—OH KNM—OH treatment ratio (%) Solid obtained Target peptide 90.4% 89.0% 94.2% 93.0% after ratio (%) treatment Increased point of −1.1 −2.2 3.3 2.0 target peptide ratio (%) (9) H—FRV (10) H—FRV Before Target peptide 93.6% 94.3% 85.2% 93.7% DEEFQSPF DEEFQSPFA treatment ratio (%) ASQSRGYF SQSRGYFLF Solid obtained Target peptide 92.9% 95.3% 96.8% 97.7% LFRPRN— RRN—NH₂ after ratio (%) NH₂ treatment Increased point of −0.7  1.0 11.6  4.0 target peptide ratio (%)

The increase points of the target peptide ratio (%) were larger in the cases where the sulfonic acid compounds were used than in the cases where the hydrochloric acid and sulfuric acid were used, which indicates that the sulfonic acid compounds showed an excellent effect in the purification of the target peptide.

Examination 4: Comparison with Carboxylic Acid Compounds

Using the sulfonic acid compounds or carboxylic acid compounds and the target peptides and analogue peptides, shown in the tables below, the increased points of the target peptide ratio (%) in the obtained solid were calculated in the same way as described above.

The results are shown in the tables below.

TABLE 8 Target peptide Analogue peptide

(9) H—FRVD (10) H—FRVD Before Target 92.2% 95.0% 92.3% 95.6% EEFQSPFAS EEFQSPFASQ treatment peptide QSRGYFLFR SRGYFLFRRN— ratio PRN—NH₂ NH₂ (%) Solid Target 96.5% 93.6% 97.1% 93.3% obtained peptide after ratio treatment (%) Increased point of 4.3 −1.4 4.8 −2.3 target peptide ratio(%)

TABLE 9 Target peptide Analogue peptide

(9) H—FRVDEEF (10) H—FRVDEEF Before Target peptide 91.8% 94.8% QSPFASQSRGYF QSPFASQSRGYFL treatment ratio (%) LFRPRN—NH₂ FRRN—NH₂ Solid obtained Target peptide 96.2% 93.4% after treatment ratio (%) Increased point of 4.4 −1.4 target peptide ratio (%)

The increased points of the target peptide ratio (%) were larger in the cases where the sulfonic acid compounds were used than in the cases where the carboxylic acid compounds were used, which indicates that the sulfonic acid compounds showed an excellent effect in the purification of the target peptide.

Examination 5: Effects of Various Sulfonic Acid Compounds-(1)

When the sulfonic acid compounds, target peptides, and analogue peptides shown in the tables below were used, the target peptide ratio (%) in some of the solids could not be calculated due to analytical problems. Therefore, the change in the target peptide ratio (%) in the filtrate combined with the washings obtained after treatment was calculated as “decreased point of target peptide ratio (%)” using the following Equation (3). Since the concentrations of the target peptide and analogue peptide before and after the treatment are unknown, and the HPLC sensitivities of the target peptide and analogue peptide are not the same, it is not possible to convert the decreased point of target peptide ratio (%) in the filtrate to the increased point of the target peptide ratio (%) in the solid. However, the decrease of the target peptide ratio in the filtrate means the increase of the target peptide ratio in the solid.

Decreased point of target peptide ratio (%)=(Target peptide ratio (%) in filtrate obtained after treatment)−(Target peptide ratio (%) of before treatment)  Equation 3):

The results are shown in the table below.

TABLE 10 Target peptide Analogue peptide

(11) H—GG (11) H—G Before Target peptide 77.0% 69.7% 72.9% GRG—NH₂ GGG—NH₂ treatment ratio (%) Filtrate Target peptide 70.2% 69.4% 67.0% obtained ratio (%) after treatment Decreased point of  6.8  0.3  5.9 target peptide ratio (%) (12) Ac-A (12) Ac- Before Target peptide 94.5% 94.4% 92.4% LRAL—NH₂ ALAL—NH₂ treatment ratio (%) Filtrate Target peptide 86.4% 79.2% 82.4% obtained ratio (%) after treatment Decreased point of  8.1 15.2 10.0 target peptide ratio (%) (8) H—YER (13) H—Y Before Target peptide 91.1% 91.8% 91.8% AKSNM—OH ERKSNM— treatment ratio (%) OH Filtrate Target peptide 75.8% 76.5% 72.8% obtained ratio (%) after treatment Decreased point of 15.3 15.3 19.0 target peptide ratio (%) (14) H—Y Before Target peptide 89.8% 90.7% 90.5% ERASNM— treatment ratio (%) OH Filtrate Target peptide 78.3% 82.5% 83.0% obtained ratio (%) after treatment Decreased point of 11.5  8.2  7.5 target peptide ratio (%)

TABLE 11 Target peptide Analogue peptide

(5) H—HAEG (5) H—HAEG Before Target 80.9% 81.2% 80.8% TFTSDVSSY TFTSDVSSY treatment peptide LEGQAAKEF LEGQAAKEF ratio (%) IAWLVKGRG— AWLVKGRG— Filtrate Target 80.2% 79.9% 79.6% OH OH obtained peptide after treatment ratio (%) Decreased point of 0.7 1.3 1.2 target peptide ratio (%) (6) H—AGCK (6) H—AGCK Before Target 90.5% 90.0% 90.6% NFFWKTFTS NFFWKTFTS— treatment peptide C—OH OH ratio (%) Filtrate Target 89.4% 88.0% 89.4% obtained peptide after treatment ratio (%) Decreased point of 1.1 2.0 1.2 target peptide ratio (%)

TABLE 12 Target peptide Analogue peptide

(12) Ac- (12) Ac- Before Target peptide 84.0% 82.6% 82.6% 79.0% ALRAL— ALAL— treatment ratio (%) NH₂ NH₂ Filtrate Target peptide 73.5%  8.0%  4.5% 18.4% obtained ratio (%) after treatment Decreased point of 10.5 74.6  78.1  60.6  target peptide ratio (%) (13) Ac- (15) Ac- Before Target peptide 83.9% 81.2% 82.3% 82.5% ALRAL— ALAL— treatment ratio (%) OH OH Filtrate Target peptide 78.1% 77.5% 76.7% 76.6% obtained ratio (%) after treatment Decreased point of  5.8 3.7 5.6 5.9 target peptide ratio (%) (8) H—Y (8) H—Y Before Target peptide 90.9% 91.9% 91.9% 91.8% ERAKSN ERKSN treatment ratio (%) M—OH M—OH Filtrate Target peptide 78.3% 80.9% 77.3% 77.3% obtained ratio (%) after treatment Decreased point of 12.6 11.0  14.6  14.5  target peptide ratio (%) (14) H— Before Target peptide 92.3% 90.7% 91.0% 91.1% YERASN treatment ratio (%) M—OH Filtrate Target peptide 84.7% 84.0% 83.7% 81.6% obtained ratio (%) after treatment Decreased point of  7.6 6.7 7.3 9.5 target peptide ratio (%) (16) H— Before Target peptide 91.3% 91.3% 92.1% 92.0% YERAKS treatment ratio (%) M—OH Filtrate Target peptide 80.1% 89.5% 89.6% 87.0% obtained ratio (%) after treatment Decreased point of 11.2 1.8 2.5 5.0 target peptide ratio (%)

TABLE 13 Target peptide Analogue peptide

(8) H—Y (13) H— Before Target 91.9% 91.8% 91.6% 91.9% ERAKSN YERKSN treatment peptide M—OH M—OH ratio (%) Filtrate Target 84.6% 71.3% 65.4% 75.5% obtained after peptide treatment ratio (%) Decreased point of 7.3 20.5 26.2 16.4  target peptide ratio (%) (14) H— Before Target 90.4% 90.5% 92.5% 91.0% YERASN treatment peptide M—OH ratio (%) Filtrate Target 88.4% 79.5% 74.1% 82.4% obtained after peptide treatment ratio (%) Decreased point of 2.0 11.0 18.4 8.6 target peptide ratio (%) (14) H— (17) H— Before Target 89.5% 90.9% 90.0% 90.7% ALRALR ALALRA treatment peptide ALR—OH LR—OH ratio (%) Filtrate Target 88.3% 85.7% 88.9% 85.9% obtained after peptide treatment ratio (%) Decreased point of 1.2  5.2  1.1 4.8 target peptide ratio (%) (6) H—A (6) H—A Before Target 90.0% 90.5% 89.8% 90.5% GCKNFF GCKNFF treatment peptide WKTFTS WKTFTS— ratio (%) C—OH OH Filtrate Target 85.9% 90.4% 88.9% 89.9% obtained after peptide treatment ratio (%) Decreased point of 4.1  0.1  0.9 0.6 target peptide ratio (%)

TABLE 14-1 Target peptide Analogue peptide

(15) Ac-GGRGG— (18) Ac-GGGG— Before Target peptide 93.7% 92.6% 91.2% NH₂ NH₂ treatment ratio (%) Filtrate obtained Target peptide 74.0% 69.3% 67.9% after treatment ratio (%) Decreased point of 19.7 22.3 23.3 target peptide ratio (%) (7) H—AQKLRAS (19) H—QKLRAS Before Target peptide 92.8% 92.5% 91.8% D—OH D—OH treatment ratio (%) Filtrate obtained Target peptide 36.5% 40.2% 20.6% after treatment ratio (%) Decreased point of 56.3 52.3 71.2 target peptide ratio (%) (20) H—AQKLRS Before Target peptide 92.8% 92.1% 92.5% D—OH treatment ratio (%) Filtrate obtained Target peptide 74.3% 73.3% 26.6% after treatment ratio (%) Decreased point of 18.5 18.8 65.9 target peptide ratio (%) (21) H—AQKLRA Before Target peptide 91.4% 91.0% 90.7% S—OH treatment ratio (%) Filtrate obtained Target peptide 66.8% 65.9% 46.6% after treatment ratio (%) Decreased point of 24.6 25.1 44.1 target peptide ratio (%)

TABLE 14-2 Target peptide Analogue peptide

(8) H—YERAKSN (22) H—ERAKSN Before Target peptide 94.3% 94.2% 94.0% M—OH M—OH treatment ratio (%) Filtrate obtained Target peptide 91.7% 91.8% 93.7% after treatment ratio (%) Decreased point of 2.6 2.4 0.3 target peptide ratio (%) (13) H—YERKSN Before Target peptide 91.8% 91.9% 90.6% M—OH treatment ratio (%) Filtrate obtained Target peptide 71.6% 75.7% 79.4% after treatment ratio (%) Decreased point of 20.2  16.2  11.2  target peptide ratio (%) (23) H—YERAKS Before Target peptide 87.8% 87.1% 84.8% N—OH treatment ratio (%) Filtrate obtained Target peptide 86.6% 85.5% 77.7% after treatment ratio (%) Decreased point of 1.2 1.6 7.1 target peptide ratio (%) (6) H—AGCKNFF (6) H—AGCKNFF Before Target peptide 90.3% 90.4% 90.20%  WKTFTSC—OH WKTFTS—OH treatment ratio (%) Filtrate obtained Target peptide 89.2% 87.2% 90.16%  after treatment ratio (%) Decreased point of 1.1 3.2  0.04 target peptide ratio (%)

TABLE 15-1 Target peptide Analogue peptide

(13) Ac-ALRAL— (15) Ac-ALAL— Before Target peptide 82.3% 81.4% 82.5% OH OH treatment ratio (%) Filtrate obtained Target peptide 78.3% 76.8% 76.6% after treatment ratio (%) Decreased point of 4.0  4.6  5.9 target peptide ratio (%) (12) Ac-ALRAL— (12) Ac-ALAL— Before Target peptide 81.5% 82.3% 79.0% NH₂ NH₂ treatment ratio (%) Filtrate obtained Target peptide 50.4% 63.4% 18.4% after treatment ratio (%) Decreased point of 31.1  18.9 60.6 target peptide ratio (%) (7) H—AQKLRAS (24) H—AQKRAS Before Target peptide 89.4% 89.9% 96.5% D—OH D—OH treatment ratio (%) Filtrate obtained Target peptide 82.9% 78.1% 74.5% after treatment ratio (%) Decreased point of 6.5 11.8 22.0 target peptide ratio (%) (8) H—YERAKSN (13) H—YERKSN Before Target peptide 91.5% 91.8% 91.8% M—OH M—OH treatment ratio (%) Filtrate obtained Target peptide 76.1% 76.8% 77.3% after treatment ratio (%) Decreased point of 15.4  15.0 14.5 target peptide ratio (%) (14) H—YERASN Before Target peptide 90.7% 90.6% 91.1% M—OH treatment ratio (%) Filtrate obtained Target peptide 83.8% 83.7% 81.6% after treatment ratio (%) Decreased point of 6.9  6.9  9.5 target peptide ratio (%)

TABLE 15-2 Target peptide Analogue peptide

(3) H—VIRALRR (3) H—VIRALRA Before Target peptide 89.2% 89.4%  88.9% ALVALRALR—OH LVALRALR—OH treatment ratio (%) Filtrate obtained Target peptide 87.8% 89.0%  87.5% after treatment ratio (%) Decreased point of 1.4 0.4 1.4 target peptide ratio (%) (16) H—HSDGTF (30) H—HSDGTF Before Target peptide 87.1% 87.3%  82.9% TSELSRLREGAR TSELSRLEGARL treatment ratio (%) LQRLLQGLV—NH₂ QRLLQGLV—NH₂ Filtrate obtained Target peptide 36.5% 64.4%  74.6% after treatment ratio (%) Decreased point of 50.6  22.9  8.3 target peptide ratio (%) (6) H—AGCKNFF (6) H—AGCKNFF Before Target peptide 91.5% 90.2% 90.309% WKTFTSC—OH WKTFTS—OH treatment ratio (%) Filtrate obtained Target peptide 85.0% 87.6% 90.307% after treatment ratio (%) Decreased point of 6.5 2.6  0.002 target peptide ratio (%)

TABLE 16-1 Target peptide Analogue peptide

(13) Ac- (15) Ac- Before Target peptide 81.3% 78.6% — 82.6% ALRAL— ALAL— treatment ratio (%) OH OH Filtrate Target peptide 78.5% 67.6% — 76.6% obtrained ratio (%) after treatment Decreased point of  2.8 11.0 —  6.0 target peptide ratio (%) (15) Ac- (18) Ac- Before Target peptide 93.0% 93.5% 93.8% 92.7% GGRGG— GGGG— treatment ratio (%) NH₂ NH₂ Filtrate Target peptide 43.8% 77.9% 51.7% 56.8% obtrained ratio (%) after treatment Decreased point of 49.2 15.6% 42.1 35.9 target peptide ratio (%)

TABLE 16-2               Target peptide               Analogue peptide  

   

(7)H- (24)H- Before Target — 90.5% — 88.5% AQKLRASD- AQKRASD- treatment peptide OH OH ratio (%) Filtrate Target — 60.0% — 82.0% obtained peptide after ratio treatment (%) Decreased point — 30.5% — 6.5% of target peptide ratio (%) (27)H- Before Target 94.2% 91.7% 90.2% 91.0% AQKLASD- treatment peptide OH ratio (%) Filtrate Target 83.3% 84.5% 77.2% 76.2% obtained peptide after ratio treatment (%) Decreased point 10.9 7.2 13.0 14.8 of target peptide ratio (%) (20)H- Before Target 92.0% — 92.3% 92.1% AQKLRSD- treatment peptide OH ratio (%) Filtrate Target 85.5% — 76.7% 85.8% obtained peptide after ratio treatment (%) Decreased point 6.5 — 15.6% 6.3 of target peptide ratio (%) (21)H- Before Target 90.7% 90.5% 90.5% 90.7% AQKLRAS- treatment peptide OH ratio (%) Filtrate Target 66.2% 48.9% 74.1% 59.3% obtained peptide after ratio treatment (%) Decreased point 24.5 41.6 16.4 31.4 of target peptide ratio (%) (8)H- Before Target 90.9% 92.2% 92.3% 92.5% AKLRAD- treatment peptide OH ratio (%) Filtrate Target 40.2% ≤88.5% 76.7% 50.4% obtained peptide after ratio treatment (%) Decreased point 50.7 ≥3.7 15.6 42.1 of target peptide ratio (%)

TABLE 16-3               Target peptide               Analogue peptide  

   

(8)H- (28)H- Before Target 91.0% 91.4% 91.7% 91.3% YERAKSNM- YRAKSNM- treatment peptide OH OH ratio (%) Filtrate Target 87.2% ≤66.4% 87.4% 82.1% obtained peptide after ratio (%) treatment Decreased point of 3.8% ≥25.0% 4.3% 9.2% target peptide ratio (%) (13)H- Before Target 91.8% 91.9% 91.7% 91.5% YERKSNM- treatment peptide OH ratio (%) Filtrate Target 81.4% 81.6% 81.8% 79.9% obtained peptide after ratio (%) treatment Decreased point of 10.4 10.3 9.9 11.6 target peptide ratio (%) (16)H- Before Target 92.8% 90.7% 95.0% — YERAKSM- treatment peptide OH ratio (%) Filtrate Target ≤89.6% ≤63.4% 93.6% — obtained peptide after ratio (%) treatment Decreased point of ≥3.2 ≥27.3 1.4 — target peptide ratio (%) (23)H- Before Target 88.3% 88.4% — 88.6% YERAKSN- treatment peptide OH ratio (%) Filtrate Target 76.1% ≤84.8% — 86.8% obtained peptide after ratio (%) treatment Decreased point of 12.2 ≥3.6 — 1.8 target peptide ratio (%)

TABLE 16-4               Target peptide               Analogue peptide

 

     

(4)H- (4)H- Before Target 88.5% — — — ARLDVASEFR ARLDVASEFR treatment peptide KKWNKALSR- KKNKALSR- ratio NH₂ NH₂ (%) Filtrate Target 87 .8% — — — obtained peptide after ratio treatment (%) Decreased point 0.7% — — — of target peptide ratio (%) (16)H- (30)H- Before Target 90.8% — 83.6% — HSDGTFTSELSRLR HSDGTFTSELSRL treatment peptide EGARLQRLLQGLV- EGARLQRLLQGLV- ratio NH₂ NH₂ (%) Filtrate Target ≤86.1% — 83.4% — obtained peptide after ratio treatment (%) Decreased point ≥4.7 — 0.2 — of target peptide ratio (%) (5)H- (5)H- Before Target 81.9% 81.2% — 80.5% HAEGTFTSDVSSYLEG HAEGTFTSDVSSYLEG treatment peptide QAAKEFIAWLVKGRG- QAAKEFAWLVKGRG- ratio OH OH (%) Filtrate Target 74.9% 80.7% — 80.1% obtained peptide after ratio treatment (%) Decreased point 7.0 0.5 — 0.4 of target peptide ratio (%) (6)H- (6)H- Before Target 90.9% 90.7% 90.3% 90.3% AGCKNFFWKTFTSC- AGCKNFFWKTFTS- treatment peptide OH OH ratio (%) Filtrate Target 89.2% 88.6% 85.3% 88.6% obtained peptide after ratio treatment (%) Decreased point 1.7 2.1 5.0% 1.7 of target peptide ratio (%) (17)Pyr- (26)Pyr- Before Target — 89.9% 89.0% 89.0% HWSYILRP- HWSYLLRP- treatment peptide NH₂ NH₂ ratio (%) Filtrate Target — 89.7% 87.5% 86.9% obtained peptide after ratio treatment (%) Decreased point — 0.2 1.5 2.1 of target peptide ratio (%)

TABLE 17

De- Target peptide creased ratio (%) point Filtrate of obtained target Before after peptide treat- treat- ratio Target peptide Analogue peptide ment ment (%) (5)H- (5)H- 80.6% 80.3% 0.3 HAEGTFTSDVSSYLEGQAAKEFIAWLVKGRG- HAEGTFTSDVSSYLEGQAAKEFAWLVKGRG- OH OH (6)H-AGCKNFFWKTFTSC-OH (6)H-AGCKNFFWKTFTS-OH 90.3% 89.7% 0.6 (7)H-AQKLRASD-OH (20)H-AQKLRSD-OH 92.4% 77.9% 14.5 (21)H-AQKLRAS-OH 90.1% 68.3% 21.8 (8)H-YERAKSNM-OH (13)H-YERKSNM-OH 91.3% 73.8% 17.5 (14)H-YERASNM-OH 90.5% 82.3% 8.2 (16)H-YERAKSM-OH 92.0% 88.3% 3.7 (22)H-ERAKSNM-OH 94.3% 90.8% 3.5 (11)H-GGGRG-NH₂ (11)H-GGGG-NH₂ 74.7% 72.3% 2.4

Examination 6: Effects of Various Sulfonic Acid Compounds-(2)

The increased points of the target peptide ratio (%) in the obtained solid were calculated in the same way as described above using the acid compounds, the target peptides, and the analogue peptides shown in the tables below.

The results are shown in the tables below.

TABLE 18               Target peptide               Analogue peptide

         

 

       

(9)H- (10)H- Before Target 91.8% 93.0% 91.8% 94.6% FRVDEEFQSPFAS FRVDEEFQSPFAS treatment peptide QSRGYFLFRPRN- QSRGYFLFRRN- ratio NH₂ NH₂ (%) Solid Target 96.2% 94.9% 96.9% 94.8% obtained peptide after ratio treatment (%) Increased point 4.4 1.9 5.1 0.2 of target peptide ratio (%) (4)H- (4)H- Before Target 88.5% 88.5% 88.5% 88.5% ARLDVASEFRKKWNKALSR- ARLDVASEFRKKNKALSR- treatment peptide NH₂ NH₂ ratio (%) Solid Target 92.6% 90.8% 92.5% 89.3% obtained peptide after ratio treatment (%) Increased point 4.1 2.3 4.0 0.8 of target peptide ratio (%) (6)H- (6)H- Before Target 90.5% 89.9% 90.2% 90.3% AGCKNFFWKTFTSC- AGCKNFFWKTFTS- treatment peptide OH OH ratio (%) Solid Target 93.0% 90.4% 93.6% 90.3% obtained peptide after ratio treatment (%) Increased point 2.5 0.5 3.4 0.0 of target peptide ratio (%)

TABLE 19                     Target peptide                     Analogue peptide

   

(6)H- (6)H- Before Target 91 .8% 90.3% AGCKNFFWKTFTSC- AGCKNFFWKTFTS- treatment peptide OH OH ratio (%) Solid Target 91.9% 93.7% obtained peptide after ratio treatment (%) Increased point 0.1 3.4 of target peptide ratio (%)

TABLE 20             Target peptide             Analogue peptide  

(17)Pyr- (26)Pyr- Before Target 90.0% 88.8% 89.1% HWSYILRP- HWSYLLRP- treatment peptide NH₂ NH₂ ratio (%) Solid Target 95.0% 93.6% 96.6% obtained peptide after ratio treatment (%) Increased point 5.0 4.8 7.5 of target peptide ratio (%)           Target peptide           Analogue peptide

         

(17)Pyr- (26)Pyr- Before Target 89.5% 89.3% HWSYILRP- HWSYLLRP- treatment peptide NH₂ NH₂ ratio (%) Solid Target 93.4% 90.6% obtained peptide after ratio treatment (%) Increased point 3.9 1.3 of target peptide ratio (%) Pyr- =

1 = D-Leu

TABLE 21                 Target peptide                 Analogue peptide  

             

(17)Pyr- (31)Pyr- Before Target 89.1% 88.7% 89.7% HWSYILRP- HWSYILLRP- treatment peptide NH₂ NH₂ ratio (%) Solid Target 94.8% 93.0% 92.9% obtained peptide after ratio treatment (%) Increased point 5.7% 4.3% 3.2% of target peptide ratio (%)

TABLE 22                       Target peptide                       Analogue peptide    

 

       

(18)H- (32)H- Before Target 94.7% 95.3% 94.8% 95.2% HVTTV- VTTV- treatment peptide NH₂ NH₂ ratio (%) Solid Target 98.5% 99.3% 97.6% 98.4% obtained peptide after ratio treatment (%) Increased point 3.8 4.0 2.8 3.2 of target peptide ratio (%) (33)H- Before Target 89.3% 88.9% 90.0% 93.4% hVTTV- treatment peptide NH₂ ratio (%) Solid Target 91.2% 92.6% 93.8% 98.0% obtained peptide after ratio treatment (%) Increased point 1.9 3.7 3.8 4.6 of target peptide ratio (%) h = D-His

TABLE 23                 Target peptide                 Analogue peptide        

 

     

(19)H- (34)H- Before Target 91.2% 91.2% 90.7% 91.1% YERAKSNM- YERAKSNL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 92.2% 91.3% 93.5% 91.4% obtained peptide after ratio treatment (%) Increased point 1.0 0.1 2.8 0.3 of target peptide ratio (%) (6)H- (35)H- Before Target 74.5% 76.6% 76.6% 74.0% AGCKNFFWKTFTSC- AGcKNFFWKTFTSC- treatment peptide OH OH ratio (%) Solid Target 76.6% 76.8% 77.1% 78.1% obtained peptide after ratio treatment (%) Increased point 2.1 0.2 0.5 4.1 of target peptide ratio (%) c = D-Cys

TABLE 24               Target peptide               Analogue peptide          

 

   

(19)H- (34)H- Before Target 91.3 91.1 91.2 92.0 YERAKSNM- YERAKSNL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 92.3 91.4 92.2 92.2 obtained peptide after ratio treatment (%) Increased point 1.0 0.3 1.0 0.2 of target peptide ratio (%) (6)H- (35)H- Before Target 76.1 74.0 74.0 76.6 AGCKNFF AGcKNFF treatment peptide WKTFTSC- WKTFTSC- ratio OH OH (%) Solid Target 76.8 78.1 77.7 77.2 obtained peptide after ratio treatment (%) Increased point 0.7 4.1 3.7 0.6 of target peptide ratio (%)

TABLE 25                     Target peptide                     Analogue peptide

(19)H- (34)H- Before Target 91.2 91.1 91.3 YERAKSNM- YERAKSNL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 91.5 91.2 92.3 obtained peptide after ratio treatment (%) Increased point 0.3 0.1 1.0 of target peptide ratio (%) (6)H- (35)H- Before Target 74.2 75.6 76.6 AGCKNFFWKTFTSC- AGcKNFFWKTFTSC- treatment peptide OH OH ratio (%) Solid Target 77.2 79.2 77.8 obtained peptide after ratio treatment (%) Increased point 3.0 3.6 1.2 of target peptide ratio (%)

TABLE 26               Target peptide               Analogue peptide

(6)H- (35)H- Before Target 76.9 74.9 AGCKNFFWKTFTSC- AGcKNFFWKTFTSC- treatment peptide OH OH ratio (%) Solid Target 77.1 75.3 obtained peptide after ratio treatment (%) Increased point 0.2 0.4 of target peptide ratio (%)

TABLE 27               Target peptide               Analogue peptide    

(20)H- (36)H- Before Target 79.8% 80.2% 78.8% VKRESYSGVT- VKRESYSGV- treatment peptide NH₂ NH₂ ratio (%) Solid Target 88.1% 80.8% 84.5% obtained peptide after ratio treatment (%) Increased point 8.3 0.6 5.7 of target peptide ratio (%) (21)H- (37)H- Before Target 92.9% 92.9% 93.0% RAVLP- RALP- treatment peptide OH OH ratio (%) Solid Target 93.7% 96.2% 95.1% obtained peptide after ratio treatment (%) Increased point 0.8 3 .3 2.1 of target peptide ratio (%) (27)Ac- (1)Ac- Before Target 92.3% 91.7% 93.5% YHYPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 99.1% 93.8% 99.0% obtained peptide after ratio treatment (%) Increased point 6.8 2.1 5.5 of target peptide ratio (%) (28)Ac- (1)Ac- Before Target 90.7% 91.2% 90.9% Y(MeK)YPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 93.0% 93.2% 98.1% obtained peptide after ratio treatment (%) Increased point 2.3 2.0 7.2 of target peptide ratio (%) MeK = α-Methyllysine

TABLE 28                     Target peptide                     Analogue peptide

     

 

   

(21)H- (37)H- Before Target 92.9% 92.7% 94.5% 93.0% RAVLP- RALP- treatment peptide OH OH ratio (%) Solid Target 94.0% 96.8% 98.2% 94.3% obtained peptide after ratio treatment (%) Increased point 1.1 4.1 3.7 1.3 of target peptide ratio (%) (27)Ac- (1)Ac- Before Target 92.3% 93.5% 93.5% 93.7% YHYPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 94.1% 95.4% 94.4% 95.9% obtained peptide after ratio treatment (%) Increased point 1.8 1.9 0.9 2.2 of target peptide ratio (%) (28)Ac- (1)Ac- Before Target 91.0% 90.2% 90.7% 91.1% Y(MeK)YPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 91.5% 92.3% 92.0% 94.1% obtained peptide after ratio treatment (%) Increased point 0.5 2.1 1.3 3.0 of target peptide ratio (%) MeK = α-Methyllysine

TABLE 29 Target peptide Analogue peptide

(22)H- (38)H- Before Target 55.7% 66.6% 66.2% (RC8)RRR (RC8)RRRR treatment peptide ratio ((Me)F)R(SC5)- (SC5)-NH₂ (%) NH₂ Solid obtained Target 67.7% 68.2% 77.3% after peptide ratio treatment (%) Increased point of target 12.0    1.6   11.1    peptide ratio (%) (27)Ac- (1)Ac- Before Target 92.3% 92.7% 92.8% YHYPEL-NH₂ YYPEL- treatment peptide ratio NH₂ (%) Solid obtained Target 93.7% 93.2% 94.2% after peptide ratio treatment (%) Increased point of target 1.4   0.5   1.4   peptide ratio (%) (28)Ac- (1)Ac- Before Target 91.3% 91.1% 91.0% Y(MeK)YPEL- YYPEL- treatment peptide ratio NH₂ NH₂ (%) Solid obtained Target 91.8% 91.5% 94.5% after peptide ratio treatment (%) Increased point of target 0.5   0.4   3.5   peptide ratio (%)

(Me) F═N-Methylphenylalanine,

MeK = α-Methyllysine

TABLE 30 Target peptide Analogue peptide

(27)Ac- (1)Ac- Before Target 92.5% 92.3% 92.8% 92.5% YHYPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 95.6% 98.7% 96.7% 95.7% obtained peptide after ratio treatment (%) Increased point of 3.1   6.4   3.9   3.2   target peptide ratio (%)

TABLE 31 Target peptide Analogue peptide

(28)Ac- (1)Ac- Before Target 91.9% 91.2% 91.1% 91.0% Y(MeK) YYPEL- treatment peptide YPEL- NH₂ ratio NH₂ (%) Solid Target 99.2% 95.0% 94.4% 96.3% obtained peptide after ratio treatment (%) Increased point of 7.3   3.8   3.3   5.3   target peptide ratio (%) MeK = α-Methyllysine

TABLE 32 Target peptide Analogue peptide

(27)Ac- (1)Ac- Before Target 93.6% 92.3% 92.5% 92.3% YHYPEL- YYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 94.7% 94.1% 92.9% 93.8% obtained peptide after ratio treatment (%) Increased point of 1.1   1.8   0.4   1.5   target peptide ratio (%) (28)Ac- (1)Ac- Before Target 90.8% 92.4% 91.1% 91.9% Y(MeK) YYPEL- treatment peptide YPEL-NH₂ NH₂ ratio (%) Solid Target 91.3% 92.6% 91.3% 92.1% obtained peptide after ratio treatment (%) Increased point of 0.5   0.2   0.2   0.2   target peptide ratio (%) (23)Ac- (39)Ac- Before Target 93.1% 92.3% 92.4% 92.7% HYFYPEL- HYYPEL- treatment peptide NH₂ NH₂ ratio (%) Solid Target 95.2% 99.7% 95.0% 9.4% obtained peptide after ratio treatment (%) Increased point of 2.1   7.4   2.6   1.7   target peptide ratio (%) MeK = α-Methyllysine

TABLE 33 Target peptide Analogue peptide

(24)H- (40)H- Before Target 93.7% 92.8% 92.4% WPVTLNAQTID- PVTLNAQTID- treatment peptide NH₂ NH₂ ratio (%) Solid Target 94.2% 93.2% 93.3% obtained peptide after ratio treatment (%) Increased point of 0.5   0.4   0.9   target peptide ratio (%)

TABLE 34 Target peptide Analogue peptide

(25)H- (41)H- Before Target 95.5% 92.6% 92.9% T((Me)G) ((Me)G)RK treatment peptide RK(Dap)H- (Dap)H- ratio OH OH (%) Solid Target 96.7% 94.3% 94.9% obtained peptide after ratio treatment (%) Increased point of 1.2   1.7   2.0   target peptide ratio (%) (Me)G = N-Methylglycine

As shown in Tables 5 to 34, the target peptide ratios in the obtained solid were increased (or the target peptide ratios in the obtained filtrate were decreased), and the sulfonic acid compounds showed excellent effects in the purification of various target peptides.

Test Example 2: Evaluation of Solvent-1

The crude target peptide ((8)H-YERAKSNM-OH) and the crude analogue peptide ((13)H-YERKSNM-OH) obtained in the above 1-1 were each dissolved in water/acetonitrile=1/2 to give a crude target peptide solution or a crude analogue peptide solution (10 mM, assuming 100% purity of each peptide).

The acid compound:

was dissolved in water to give a 30 mM acid compound solution.

The crude target peptide solution (1 μmol, assuming 100% purity of the target peptide) and the crude analogue peptide solution (0.1 μmol, assuming 100% purity of the analogue peptide) were mixed.

The mixture was mixed with the acid compound solution (0.9 μmol) (the resulting mixture was subjected to HPLC analysis to give a measurement value of before treatment), and then the mixture was dried by lyophilization.

To the residue was added 100 μL of the solvent shown in the tables below and shaken overnight at room temperature. The resulting slurry was subjected to centrifugal filtration (14000 rpm, 1 min), and the cake was washed with 100 μL of the solvent 2 times. The filtrate was combined with the washings.

The resulting solid and the filtrate combined with the washings were analyzed by HPLC to give the values of “solid obtained after treatment” and “filtrate obtained after treatment”.

In the same manner as described above, the decreased points of target peptide ratio (%) in the obtained filtrate combined with the washings was calculated.

In addition, the HPLC area percentage of the target peptide was calculated using the HPLC analysis results of before treatment and the solid obtained after treatment, while the peak of sulfonic acid compound was excluded from the total area.

TABLE 35 Target peptide (8) H-YERAKSNM-OH Analogue peptide (13) H-YERKSNM-OH Before Filtrate Decreased treatment obtained point of Target after treatment target peptide Target peptide peptide Solvent ratio (%) ratio (%) ratio (%) IPA 91.6% 64.9% 26.7 MeOH 91.8% 91.5%  0.3 1,4-Dioxane/Water (20/1) 91.2% 60.1% 31.1 DME/Water(20/1) 91.8% 74.9% 16.9 THF/Water (20/1) 91.8% 48.2% 43.6 IPA/Water (20/1) 91.7% 71.9% 19.8 Acetone/Water(20/1) 92.2% 70.3% 21.9 Acetonitrile/Water(20/1) 91.1% 64.4% 26.7

TABLE 36 Before Solid obtained treatment after treatment Area of target Area of target Solvent peptide (%) peptide (%) IPA 47.13 65.29 MeOH 47.47 54.74 1,4-Dioxane/Water(20/1) 49.07 70.66 DME/Water(20/1) 49.56 72.53 THF/Water (20/1) 49.61 68.26 IPA/Water(20/1) 49.47 66.80 Acetone/Water(20/1) 48.86 65.58 Acetonitrile/Water(20/1) 48.44 64.83 Area of target peptide (%) = Peak area of target peptide/(Total area − Peak area of sulfonic acid compound) × 100

As shown in Tables 35 and 36, the absolute purity and relative purity of the target peptide were increased. The results show that the sulfonic acid compound is effective in the purification of the target peptide using any of the solvents. That is, a solvent suitable for removing an analogue peptide can be selected by examining a constitution of solvents within the extent reasonably expected to do so.

Test Example 3: Scale-Up

The same target peptide, analogue peptide, and sulfonic acid compound as in Test Example 2 were used.

The crude target peptide, the crude analogue peptide, the sulfonic acid compound were each dissolved in water/acetonitrile=1/2 to give a crude target peptide solution (50 mM, assuming 100% purity of peptide), a crude analogue peptide solution (50 mM, assuming 100% purity of peptide), and a sulfonic acid compound solution (75 mM). The crude target peptide solution 1 mL (50 μmol), and the crude analogue peptide solution 0.1 mL (5 μmol) were mixed.

One milliliter of the sulfonic acid compound solution (75 μmol) was added thereto (the resulting mixture was subjected to HPLC analysis (Condition A) to give a measurement value of before treatment), and then the mixture was dried by lyophilization. To the residue was added 1 mL of IPA, the mixture was dispersed, and then lyophilized again to obtain a residue (67.35 mg).

To the residue was added 2 mL of IPA, the mixture was shaken at 700 rpm for 3 hours, and subjected to centrifugation (14000 rpm, 1 min). The solid and the supernatant were separated and each was lyophilized to give 60.74 mg of a residue derived from the solid portion, and 5.84 mg of a residue derived from the supernatant portion. Each was analyzed by HPLC (Condition A) to give the values of “after treatment”. The results are shown in the table below.

TABLE 37 Target peptide (8) H-YERAKSNM-OH Analogue peptide (13) H-YERKSNM-OH Solvent Before treatment Filtrate obtained Decreased Target peptide after treatment point of target ratio Target peptide peptide (%) ratio (%) ratio (%) IPA 91.4% 63.5% 27.9

Even when the scale was increased, similar results as in Test example 2 were obtained.

Test Example 4: Removal of Sulfonic Acid Compound

The same target peptide, analogue peptide, and sulfonic acid compound as in Test example 3 were used.

The crude target peptide, the crude analogue peptide, the sulfonic acid compound were each dissolved in water/acetonitrile=1/2 to give a crude target peptide solution (50 mM, assuming 100% purity of peptide), a crude analogue peptide solution (50 mM, assuming 100% purity of peptide), and a sulfonic acid compound solution (75 mM). One milliliter of the crude target peptide solution (50 μmol) and 0.1 mL of the crude analogue peptide (5 μmol) were mixed.

One milliliter of the sulfonic acid compound solution (75 μmol) was added thereto (the resulting mixture was subjected to HPLC analysis (Condition A) to give a measurement value of before treatment), and then the mixture was dried by lyophilization. To the residue was added 1 mL of IPA, the mixture was dispersed, and then lyophilized again to give a residue (70.93 mg).

To the residue was added 5 mL of IPA, the mixture was shaken at 700 rpm for 3.5 hours, and subjected to centrifugation (14000 rpm, 1 min). The solid and the supernatant were separated. The solid was washed with 1 mL of IPA. The solid and the supernatant combined with the washing were respectively lyophilized to give 59.58 mg of a residue derived from the solid portion, and 5.40 mg of a residue derived from the supernatant portion.

Oasis WAX Cartridge (6 cc/150 mg) (Waters) was pretreated with 1 mL of 1N aqueous solution of sodium hydroxide, 7 mL of water (purified water), and 2 mL of water/MeOH (10/1) in this order.

Fifteen point seven four milligrams of the residue derived from the solid was dissolved in 1 mL of water/MeOH (10/1), (the resulting mixture was subjected to HPLC analysis (Condition A) to give a measurement value of after treatment, where the sulfonic acid was eluted at around 5.1 min). The mixture was loaded onto the pretreated Oasis WAX Cartridge (6 cc/150 mg), and 9 mL of water/MeOH (10/1) was passed through the cartridge. The solution passed through the cartridge was analyzed by HPLC (Condition A) to confirm removal of the sulfonic acid compound and give a measurement value after removal of sulfonic acid. The solution was lyophilized to give 9.47 mg of a residue.

The following table shows the HPLC area percentage of the target peptide in the HPLC analysis of the solution before the treatment with the sulfonic acid compound, of the solid obtained after the treatment, and of the sample after removal of the sulfonic acid compound.

TABLE 38 Area of Target peptide (%) After removal of sulfonic acid Before treatment After treatment compound 42.85 61.59 76.44

${{Area}\mspace{14mu}{of}\mspace{14mu}{target}\mspace{14mu}{peptide}\mspace{11mu}(\%)} = {\frac{{Peak}\mspace{14mu}{area}\mspace{14mu}{of}\mspace{14mu}{target}\mspace{14mu}{peptide}}{\begin{matrix} \left( {{{Total}\mspace{14mu}{area}} -} \right. \\ \left. {{Peak}\mspace{14mu}{area}\mspace{14mu}{of}\mspace{14mu}{sulfonic}\mspace{14mu}{acid}\mspace{14mu}{compound}} \right) \end{matrix}} \times 100}$

Test Example 5: Evaluation of Solvent-2

The crude target peptide ((8)H-YERAKSNM-OH) and the crude analogue peptide ((23)H-YERAKSN-OH) obtained in the above 1-1 were each dissolved in water/acetonitrile=1/2 to give a crude target peptide solution and a crude analogue peptide solution (10 mM, assuming 100% purity of each peptide).

The sulfonic acid compound:

was dissolved in water to give a 50 mM sulfonic acid compound solution.

The crude target peptide solution (1 μmol, assuming 100% purity of the target peptide) and the crude analogue peptide solution (0.1 μmol, assuming 100% purity of the analogue peptide) were mixed.

The mixture was mixed with the sulfonic acid compound solution (1.5 μmol) (the resulting mixture was subjected to HPLC analysis to give a measurement value of before treatment), and then the mixture was dried by lyophilization.

To the residue was added 100 μL of the solvent shown in the tables below and the mixture was shaken overnight at room temperature. The resulting slurry was subjected to centrifugal filtration (14000 rpm, 1 min), and the cake was washed with 100 μL of the solvent 2 times. The filtrate was combined with the washings.

The resulting solid and the filtrate combined with the washings were analyzed by HPLC to give the values of “solid obtained after treatment” and “filtrate obtained after treatment”.

In the same manner as described above, the decreased points of target peptide ratio (%) in the obtained filtrate combined with the washings were calculated.

In addition, the HPLC area percentage of the target peptide was calculated using the HPLC analysis results of before treatment and the solid obtained after treatment, while regarding the solid obtained after treatment the peak of sulfonic acid compound was excluded from the total area.

The results are shown in the tables below.

As shown in the tables below, the absolute purity and relative purity of the target peptide were increased. The results show that the sulfonic acid compound is effective in the purification of the target peptide using any of the solvents.

TABLE 39 Target peptide (8) H-YERAKSNM-OH Analogue peptide (23) H-YERAKSN-OH Solvent Before Filtrate Decreased treatment obtained point of Target after target peptide treatment peptide ratio Target ratio (%) peptide (%) ratio (%) IPA   93.2% 61.3%   31.9 MeOH ≥92.4% 89.8%  ≥2.6 1,4-Dioxane/Water (20/1) ≥92.9% 77.3% ≥15.6 DME/Water (20/1) ≥92.5% 70.3% ≥22.2 IPA/Water (20/1) ≥92.7% 76.5% ≥16.2 Acetone/Water (20/1) ≥92.7% 47.1% ≥45.6 Acetonitrile/Water (20/1) ≥91.9% 32.4% ≥59.5

TABLE 40 Before Solid obtained treatment after treatment Area of target Area of target Solvent peptide (%) peptide (%) IPA 45.99 64.44 MeOH 43.91 51.47 1,4-Dioxane/Water (20/1) 46.03 65.65 DME/Water (20/1) 44.24 65. 46 THF/Water (20/1) 46.08 62.48 IPA/Water (20/1) 45.20 64.40 Acetone/Water(20/1) 46.07 60.27 Acetonitrile/Water (20/1) 43.31 62.53 Area of target peptide (%) = Peak area of target peptide/(Total area − Peak area of sulfonic acid compound) × 100

Test Example 6: Purification of Target Peptide-2

With respect to the target peptides, analogue peptides, and sulfonic acid compounds shown in the table below, the HPLC area percentage of the target peptide in the solution before treatment and in the solid obtained after treatment was calculated based on the results of the HPLC analysis performed in Test example 1, while the peak of sulfonic acid compound was excluded from the total area.

TABLE 41 Area of target peptide (%) Analogue Sulfonic acid HPLC Before Solid obtained Target peptide peptide compound condition treatment after treatment (14)H-ALRALRALR-OH (17)H-ALALRALR-OH

J 60.35 71.05 (8)H-YERAKSNM-OH (23)H-YERAKSN-OH

A 41.50 61.69 (8)H-YERAKSNM-OH (23)H-YERAKSN-OH

A 42.88 61.75 Area of target peptide (%) = Peak area of target peptide/(Total area-Peak area of sulfonic acid compound) × 100

Test Example 7: Purification of Target Peptide-3

(1) This test was performed in the same manner as Test Example 1 (paragraph [0141]), using H-AQKLRASD-OH (referred to as target peptide (7) in Table 1) as a crude analogue peptide, H-QKLRASD-OH (referred to as analogue peptide (19) in Table 1) as a crude target peptide, and the same sulfonic acid compounds as paragraph [0167](Table 14-1). The peptides were obtained in “1-1: Synthesis of Peptide (paragraphs [0082] to [0128])”.

The results are shown in the table below.

TABLE 42 Target peptide Analogue peptide

H- H- Before Target 83.3% 90.3% 91.3% QKLRASD- AQKLRASD- treatment peptide OH OH ratio (%) Filtration Target 83.0% 77.7% 32.5% obtained peptide after ratio treatment (%) Decreased point of 0.3   12.6    58.8    target peptide ratio (%) (2) Similarly, this test was performed in the same manner as Test example 1 (paragraph [0141]), using H-AQKLRASD-OH (referred to as target peptide (7) in Table 1) as a crude analogue peptide, H-AQKLRSD-OH (referred to as analogue peptide (20) in Table 1) as a crude target peptide, and the same sulfonic acid compound as paragraph [0172] (Table 16-2). The results are shown in the table below.

TABLE 43 Target peptide Analogue peptide

H- H- Before Target 76.6 AQKLRSD- AQKLRASD- treatment peptide OH OH ratio (%) Filtration Target 74.5 obtained peptide after ratio treatment (%) Decreased point of  2.1 target peptide ratio (%) (3) Similarly, this test was performed in the same manner as Test example 1 (paragraph [0141]), using H-YERAKSNM-OH (referred to as target peptide (8) in Table 1) as a crude analogue peptide, H-YERAKNM-OH (referred to as analogue peptide (9) in Table 1) as a crude target peptide, and the same sulfonic acid compounds as paragraph [0155] (Table 7). The results are shown in the table below.

TABLE 44 Target peptide Analogue peptide

H- H- Before Target 89.7 89.8 YERAKNM- YERAKSNM- treatment peptide ratio OH OH (%) Solid Target 91.1 91.3 obtained after peptide ratio treatment (%) Increased point of target  1.4  1.5 peptide ratio (%) (4) Similarly, this test was performed in the same manner as Test example 1 (paragraph [0141]), using H-YERAKSNM-OH (referred to as target peptide (8) in Table 1) as a crude analogue peptide, H-YERAKSN-OH (referred to as analogue peptide (23) in Table 1) as a crude target peptide, and the same sulfonic acid compounds as paragraph [0168] (Table 14-2). The results are shown in the table below.

TABLE 45 Target peptide Analogue peptide

H- H- Before Target 91.7 92.9 93.1 YERAKSN- YERAKSNM- treatment peptide OH OH ratio (%) Filtration Target 81.5 91.3 92.5 obtained peptide after ratio treatment (%) Decreased point of 10.2  1.6  0.6 target peptide ratio (%) (5) Similarly, this test was performed in the same manner as Test example 1 (paragraph [0141]), using H-AQKLRASD-OH (referred to as target peptide (7) in Table 1) as a crude analogue peptide, H-AQKRASD-OH (referred to as analogue peptide (24) in Table 1) as a crude target peptide, and the same sulfonic acid compound as paragraph [0172] (Table 16-2). The results are shown in the table below.

TABLE 46 Target peptide Analogue peptide

H- H- Before Target 88.5 AQKLRSD- AQKLRASD- treatment peptide OH OH ratio (%) Filtration Target 79.1 obtained peptide after ratio treatment (%) Decreased point of  9.4 target peptide ratio (%)

In Test Example 7, in order to further prove that the method of the present invention is a highly versatile peptide purification method, the molar ratio of the target peptide to the analogue peptide of Test Example 1 was reversed, that is, the analogue peptide of Test example 1 was used as a target peptide, and the target peptide of Test example 1 was used as an analogue peptide.

Specifically, Test example 1, paragraph [0167] [Table 14-1] shows the results of a model in which the target peptide (7)H-AQKLRASD-OH and analogue peptide (19)H-QKLRASD-OH were mixed in a molar ratio of about 10:1. On the other hand, Test example 7 was performed using the same sulfonic acid compounds, with a model of reversed molar ratio (theoretical value), i.e. (7)H-AQKLRASD-OH:(19)H-QKLRASD-OH=about 1:10.

In addition, regarding the following combinations of target peptide and analogue peptide in Test example 1, Test example 7 was performed using the reversed molar ratio (theoretical value), with the same sulfonic acid compounds as Test example 1:

target peptide (7)H-AQKLRASD-OH and analogue peptide (20)H-AQKLRSD-OH in paragraph [0172][Table 16-2];

target peptide (8)H-YERAKSNM-OH and analogue peptide (9)H-YERAKNM-OH in paragraph [0155][Table 7];

target peptide (8)H-YERAKSNM-OH and analogue peptide (23)H-YERAKSN-OH in paragraph [0168][Table 14-2];

target peptide (7)H-AQKLRASD-OH and analogue peptide (24)H-AQKLRSD-OH in paragraph [0172][Table 16-2].

The results of Test Example 7 clearly show that even when the mixing ratio was reversed, that is, even when the analogue peptide of Test Example 1 was used as a target peptide and the target peptide of Test Example 1 was used as an analogue peptide, the relative purity of the target peptide relative to the analogue peptide in the solid was increased (or reduced in the liquid).

Test Example 8: Effects of Various Sulfonic Acid Compounds (Removal of Multiple Analogue Peptides)

Using multiple crude analogue peptide solutions (0.1 μmol each, assuming 100% purity of peptide), the increased point of target peptide ratio (%) to each analogue peptide in the obtained solid was calculated in the same manner as in Test Example 1 (paragraph [0141]).

The results are shown in the tables below.

TABLE 47 Target peptide Analogue peptide

H- H- Before Target 95.4 95.8 95.8 96.0 AQKLRASD- QKLRASD- treatment peptide OH OH ratio (%) Solid Target 95.7 96.8 96.6 96.4 obtained peptide after ratio treatment (%) Increased point of  0.3  1.0  0.8  0.4 target peptide ratio (%) H- Before Target 98.7 95.7 95.9 95.4 AQKLRSD- treatment peptide OH ratio (%) Solid Target 99.4 97.8 97.6 97.0 obtained peptide after ratio treatment (%) Increased point of  0.7  2.1  1.7  1.6 target peptide ratio (%)

TABLE 48 Target peptide Analogue peptide

H- H- Before Target 89.0 89.6 89.7 92.0 YERAKSNM- YERASNM- treatment peptide OH OH ratio (%) Solid Target 91.5 91.4 91.3 93.8 obtained peptide after ratio treatment (%) Increased point of  2.5  1.8  1.6  1.8 target peptide ratio (%) H- Before Target 93.3 92.9 92.6 94.8 YERAKNM- treatment peptide OH ratio (%) Solid Target 95.4 95.4 95.2 96.4 obtained peptide after ratio treatment (%) Increased point of  2.1  2.5  2.6  1.6 target peptide ratio (%)

TABLE 49 Target peptide Analogue peptide

H- H- Before Target 88.1 88.8 90.1 88.6 YERAKSNM- YERASNM- treatment peptide OH OH ratio (%) Solid Target 90.4 90.4 93.8 90.3 obtained peptide after ratio treatment (%) Increased point of  2.3  1.6  3.7  1.7 target peptide ratio (%) H- Before Target 92.5 92.5 93.6 93.2 YERAKNM- treatment peptide OH ratio (%) Solid Target 96.3 95.0 96.5 95.0 obtained peptide after ratio treatment (%) Increased point of  3.8  2.5  2.9  1.8 target peptide ratio (%) H- Before Target 87.7 88.5 89.2 89.3 YERAKSN- treatment peptide OH ratio (%) Solid Target 90.0 91.5 97.4 94.2 obtained peptide after ratio treatment (%) Increased point of  2.3  3.0  8.2  4.9 target peptide ratio (%)

As shown in Tables 47 to 49, the target peptide ratios in the obtained solid were increased, and the sulfonic acid compounds showed excellent effects in the purification of various target peptides.

INDUSTRIAL APPLICABILITY

The methods of the present application can be used to purify peptides. 

1. A method for purifying a target peptide from a peptide product obtained through a peptide synthesis, wherein the target peptide is free at the N-terminus and/or comprises at least one basic amino acid residue, the method comprising: (1) mixing the peptide product with a solvent in the presence of a sulfonic acid compound to provide a solid; (2) performing a solid-liquid separation to collect the solid. 2-7. (canceled)
 8. The method of claim 1, wherein the sulfonic acid compound is of formula (I):

wherein: A is an optionally substituted C₆₋₁₀ aryl, an optionally substituted bicyclic heterocyclic group, C₂₋₃ alkenyl, or C₂₋₃ alkynyl; X is (i) a single bond, (ii) an optionally substituted C₁₋₄ alkylene, (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or (iv) C₂₋₄ alkenylene; and n is an integer in a range of from 1 to
 3. 9. The method of claim 8, wherein A is C₆₋₁₀ aryl which may be substituted; X is (i) a single bond, (ii) an optionally substituted C₁₋₄ alkylene, (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or (iv) C₂₋₃ alkenylene; and n is an integer in a range of from 1 to
 3. 10. The method of claim 8, wherein A is an optionally substituted bicyclic heterocyclic group; X is (i) a single bond, (ii) C₁₋₄ alkylene, (iii) —CO—(CH₂)_(n)— wherein the CO binds to the A, or (iv) C₂₋₃ alkenylene; and n is an integer in a range of from 1 to
 3. 11. The method of claim 8, wherein A is C₂₋₃ alkenyl; and X is C₁₋₄ alkylene.
 12. The method of claim 8, wherein A is C₂₋₃ alkynyl; and X is C₁₋₄ alkylene.
 13. The method of claim 1, wherein the target peptide has 5 to 31 amino acid residues.
 14. The method of claim 1, wherein the peptide product comprises a peptide analog.
 15. The method of claim 14, wherein the molar ratio of the peptide analog to the target peptide is 0.7 or less in the peptide product.
 16. The method of claim 1, wherein the peptide synthesis is a solid phase peptide synthesis.
 17. The method of claim 1, wherein the target peptide comprises a basic amino acid residue and is optionally free at the N-terminus.
 18. The method of claim 8, wherein A is a C₆₋₁₄ aryl optionally comprising 1 to 5 substituents independently selected from the group consisting of C₁₋₄ alkyl, —CO—C₆₋₁₀ aryl, —OH, —O—C₁₋₃ alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄ alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄ alkyl, —CF₃, and C₆₋₁₀ aryl.
 19. (canceled)
 20. The method of claim 8, wherein A is a C₆₋₁₀ aryl selected from the group consisting of phenyl, naphthyl, and indanyl, wherein the C₆₋₁₀ aryl is optionally substituted with 1 to 5 substituents independently selected from the group consisting of C₁₋₄ alkyl, —CO—C₆₋₁₀ aryl, —OH, —O—C₁₋₃ alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄ alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄ alkyl, —CF₃, and C₆₋₁₀ aryl.
 21. The method of claim 8, wherein A is an optionally substituted bicyclic heterocyclic group selected from the group consisting of 2,3,4,5-tetrahydro-1H-1-benzazepinyl, benzoxanyl, indolinyl, isoindolinyl, phthalazinyl, chromanyl, benzofuranyl, benzothiophenyl, pyrimidinyl, benzothiazolyl, quinolyl, isochromanyl, and benzotriazolyl.
 22. The method of claim 8, wherein A is a bicyclic heterocyclic group optionally substituted with 1 to 5 substituents independently selected from the group consisting of C₆₋₁₀ aryl, C₁₋₄ alkyl, —CO—C₆₋₁₀ aryl, —OH, —O—C₁₋₃ alkyl, —NO₂, —CO₂H, —CO₂—C₁₋₄ alkyl, halogen, —NH₂, —CH₂—SO₃H, —SO₃H, —CN, —CO—C₁₋₄ alkyl, —CF₃, and oxo.
 23. The method of claim 8, wherein A is

optionally substituted with one phenyl group.
 24. (canceled)
 25. The method of claim 8, wherein X is (i) a single bond, (ii) C₁₋₄ alkylene optionally substituted with one methyl group, one benzyl group or one phenyl group, or (iii) —CO—CH₂— wherein the CO binds to the A.
 26. (canceled)
 27. The method of claim 18, wherein X is (i) a single bond, (ii) C₁₋₄ alkylene optionally substituted with one methyl group, one benzyl group, or one phenyl group, or (iii) —CO—(CH₂)— wherein the CO binds to the A.
 28. The method of claim 8, wherein X is a single bond.
 29. The method of claim 23, wherein X is a single bond.
 30. The method of claim 1, wherein the sulfonic acid compound is:


31. The method of claim 1, further comprising: removing the sulfonic acid compound.
 32. The method of claim 1, wherein the method increases the molar ratio of the target peptide to an peptide analog.
 33. A method for producing the target peptide, comprising the method of claim
 1. 34-36. (canceled) 